Square Roots and the

Transcription

1 ~.... Square Roots and the Pythagorean Theorem VovM~~ry for clv~p4:er 7 Key Mathematical Vocabulary square root, p. 288 real numbers, p. 294 right triangle, p. 302 Academic Vocabulary approximate Perform calculations using given numbers that are not exact, rounding the result to reflect the inaccuracy of the given numbers. For example, see Example 1 on page 294. describe, p. 286 explain, p. 287 check, p. 293 make a conjecture, p.300 compare, p. 300 predict, p. 312

2 .0 Students understand and use such operations as taking the opposite, finding the reciprocal, taking a root, and raising to a fractional power. They understand and use the rules of exponents. Gr. 7 MG 3.3 Know and understand the Pythagorean theorem and its converse and use it to find the length of the missing side of a right triangle and the lengths of other line segments and, in some situations, empirically verify the Pythagorean theorem by direct measurement. Review Prerequisite Skills REVIEW VOCABULARY integers, p. 162 round, p. 479 perimeter, p. 488 rational numbers, p. 204 area, 488 triangle, p. 488 VOCABULARY CHECK Copy and complete the statement. 1. Numbers that can be written in the form~ where a and bare integers and b * 0 are called.1_. 2. When you approximate a number to a given place value, you are.1_ the number. 3. The numbers..., -3, -2, -1, 0, 1, 2, 3,... are called.1_. SKILLS CHECK Find the area of the square or rectangle. (Review pp. 114 and 488 for ) 4. D lm o 3.3ft D 4in. s. 6. 1m 5.5 ft 4 in. Evaluate the expression. (Review pp. 80, 114, and 182 for ) 7. ( -5) 2 8. ( ~ t Order the numbers from least to greatest. (Review pp. so and 204 for 7.2.) , 115, 11.3, , 3' -3, , 27, -2.25, 5 Evaluate the expression. (Review p. 12 for )

3 lor Finding Side Lengths of Squares Goal Find the side length of a square if you know its area. Materials graph paper Q.UESTION How can you find the side length of a square if you know its area? EXPLORE 1 Draw four squares with areas 1, 4, 9, and 16. D EE Area= 1 Area= 4 Area= 9 Area = 16 Look for a pattern in your drawings in Step 1. Copy and complete the areas and side lengths in the table below. Area of square (square units) Side length (units) ???????? 400? Write a formula that gives the relationship between a square's side lengths and its area A. Draw Conclusions 1. Does the square shown confirm one of the entries in your table from Step 2? Explain. 2. Draw a square with an area of 36 square units. What side length must you use? 3. Describe how you could use the area formula you wrote in Step 3 to find the length of a side of a square if you know its area. 4. The area of a square is 81 square units. Substitute 81 for A in the area formula you wrote in Step 3. What is the length of a side of this square? How do you know?

4 ~... Alg 2.0 Students understand and use such operations as taking the opposite, r- finding the reciprocal, taking a root, and raising to a fractional power. They understand and use the rules of exponents. EXPLORE 2 Any number you square to get a number a is called a square root of a. Because 10 2 = 100 and ( -10) 2 = 100, 10 and -10 are square roots of 100. Find a positive number, if one exists, that you can square to get each value of a listed in the table. Copy the table and complete the second row. Value of a Positive number whose square is a???? Find a negative number, if one exists, that you can square to get each value of a listed in the table. Add and complete the third row of the table. Value of a Positive number whose square is a Negative number whose square is a???????? Draw Conclusions In Exercises 5-7, write the number as {a} the square of a positive integer and { b} the square of a negative integer Notice that in Exercises 5-7, each number can be written as the square of two integers, so each number has two square roots. In Exercise 4, you wrote a formula for the area of a square whose area was 81 square inches. Are there two side lengths in that situation? How is Exercise 4 different from Exercises 5-7? 9. In Exercises 5-7, you saw that a positive number a has two square roots. a. Consider the case when a is 0. How many square roots does 0 have? b. Consider the case when a is negative. When you square a positive number, is the result positive or negative? When you square a negative number, is the result positive or negative? Will you ever get a square that is negative? Can a negative number have a square root? Explain. 7.1 Find Square Roots of Perfect Squares

5 Find Square Roots of Perfect Squares VOCABULARY and CONCEPTS A square root of a real number a is a real number b such that b 2 = a. The square of an integer is called a perfect square. Square Roots A square root is written with the symbol Y. Any positive number a has two square roots, a positive (principal) square root, Va, and a negative square root, - Ya. Zero has one square root: Yo = 0. Negative numbers have no real square roots. The two square roots of a positive number can be written together with the symbol ± (plus or minus): You can read ±\136 as the positive and negative square roots of 36. EXAMPLE 1 F~~ s1u-a,;r~ Rootf Find the two square roots of the number. a. 49 b. 169 Solution a. Because 7 2 = 49 and ( -7) 2 = 49, the two square roots of 49 are 7 and - 7. b. Because 13 2 = 169 and (-13) 2 = 169, the two square roots of 169 are 13 and -13. EXAMPLE 2 Evaluate the expression. a. v'460 Solution a. v'460 = 20 b. -m = -4 b. -m The positive square root of 400 is 20. The negative square root of 16 is -4. c. ±Vsl c. ±Vsl = ±9 The positive and negative square roots of 81 are 9 and -9. Practice for Examples 1 and What are the two square roots of 144? Evaluate the expression. 2. v2s V ±V Yo Chapter 7 Square Roots and the Pythagorean Theorem

6 ~..._ Alg 2.0 Students understand and use such operations as taking the opposite, ~ finding the reciprocal, taking a root, and raising to a fractional power. They understand and use the rules of exponents. EXAMPLE 3 F ~iatj tl.t SUe- L e,ftj t/-v The area of a square is 900 square inches. Find the side length of the square. s 2 =A i = 900 s = ±V900 s = 30 Formula for area of a square Substitute 900 for A. Definition of square root Choose positive square root; length is nonnegative. ~Answer The side length of the square is 30 inches. EXAMPLE 4 Us iatj Area. to F i,;/1ai P e,r ~te,r A landscaper wants to put fencing around two square gardens that are next to each other as shown. The areas of the gardens are 64m 2 and 100m 2. What is the length of fencing that will be needed? Solution Notice that the perimeter is formed by three sides of the small square, three sides of the large square, and part of the fourth side of the large square. The areas of the squares are 64m 2 and 100m 2. Use the area formula to find the side lengths of the small garden and of the large garden. Small garden i = 64 s = 8 Large garden s 2 = 100 s = 10 The distance around 3 sides of the small garden is = 24 m. The distance around 3 sides of the large garden is = 30 m. The remaining part of the perimeter has length 10-8 = 2 m. ~Answer The distance around the figure is = 56, so 56 meters of fencing will be needed. Practice for Examples 3 and 4 Find the side length of a square with the given area square miles square meters 8. Suppose the area of the small garden in Example 4 is increased to 81 m 2 instead. How much fencing will be needed now? 7.1 Find Square Roots of Perfect Squares

7 Pract1ce Extra Practice p. 504 Find the two square roots of the number Evaluate the expression. 9. Y V m 13. Vs vm 15. ±V V9 18. V V ±\ Vi V16oo 16. ±V ViOO 24. -' You are considering buying a square area rug that has an area of 25 square feet. Find the side length of the area rug. 26. The infield of a baseball field is a square, as shown in the figure. If its area is 8100 square feet, what is the distance from first base to second base? 27. A square ice skating rink has an area of 2500 square feet. What is the perimeter of the rink? 28. You are going to put carpet binding on all four sides of a square piece of leftover carpet. The area of the carpet is 9 square feet. What length of carpet binding do you need? 29. The U.S. Department of Transportation determines the sizes of the traffic control signs that you see along the roadways. If you ignore the rounded corners, the square Alabama state route sign at the right has an area of 576 square inches. Find the side length of the sign. In Exercises 30-33, use the following information. Elisa wants to build a sandbox for her cousins. She wants the sandbox to be in the shape of a square with an area of 121 square feet. Elisa has several boards with a combined length of 45 feet to use as sides. 30. Find the side length (in feet) of the sandbox. 31. Find the perimeter of the sandbox. 32. Does Elisa have enough boards to make the sides of the sandbox? Explain. 33. Elisa wants to use boards that are 6 inches high and fill the sand to the top of the boards. What will the volume of the sandbox be? 34. REASONING Evaluate each expression. Describe the pattern. vt, v'l+3, V , V , V ,... Chapter 7 Square Roots and the Pythagorean Theorem

8 classzone.com Find the two square roots of the number Evaluate the expression. 9. v' V25oo 11. -Vi% Vi6 14. v' ±v' V V v 49oo V v v%1 24. Find the two square roots of the number v o v o.s1 31. vt Evaluate the expression for the given value of x Vx when x = Vx when x = Vx when x = vx - 1 whenx = A community garden is in the shape of a square and covers an area of 3600 square feet. Find the side length of the garden. 38. The first, second, and third bases on a baseball field are square canvas bags that each have an area of 225 square inches. What is the side length of a base? 39. You are considering buying a square wall poster that has an area of 6.25 square feet. Find the side length of the wall poster. 40. You are building a square shadow box whose front has an area of 36 square inches. The box will be divided into 9 square compartments of equal size. What is the side length of each compartment? 41. The area inside the square picture frame shown is 100 square inches. The area of the space for a square photograph is 25 square inches. The frame creates a uniform border all around the photograph. What is the width of the border? 42. A park occupies one square-shaped city block. The city wants to put a fence around the park. The park has an area of 960,400 square feet. The city already has 3000 feet of fencing. How much more will the city need to purchase? 43. REASONING For a nonnegative value of a, what is ( vap? Explain your reasomng v'324 ±m ±Vi69 ± V v ? 7.1 Find Square Roots of Perfect Squares

9 lor Using Squares to Approximate Square Roots Goal Materials Use a model to approximate a graph paper scissors square root. tape colored pencils Q.UESTION How can you use unit squares to approximate a square root? You can build squares using unit squares. Model: D EE llij Size: 1 by 1 2 by 2 3 by 3 4 by 4 Number of unit squares: The length of a side of any square is the positive square root of the number of unit squares the square contains. EXPLORE You can build squares that have areas close to 14 unit squares. The lengths of the sides of these squares will be approximations of ill. Build the largest square that you can using 14 unit squares. The 14 squares are more than 9 squares (3 by 3) and less than 16 squares (4 by 4). So, the largest square you can build is 3 by 3, with 5 unit squares left over. D Imagine building a slightly larger square with an area of 14 by cutting up the leftover squares and placing them along two sides to fill the red region shown. Divide the 5 leftover squares into 2 3 = 6 equal pieces and place them on the red region as shown. (You may need to turn some of the pieces.) A small corner of the red region will be left uncovered _ by 3 +.1_

10 ~... Alg 2.0 Students understand and use such operations as taking the opposite, ~ finding the reciprocal, taking a root, and raising to a fractional power. They understand and use the rules of exponents. m Repeat Steps 2 and 3, but this time divide the 5leftover - squares into = 7 equal pieces and place them on the red region as shown. The seventh piece can be used to fill the small corner, but some of this piece will be left over. Draw Conclusions Use your results from the Explore section. Write your answers using fractions and mixed numbers. 1. In Step 3, you divided 5 unit squares into 6 equal pieces. The length of each piece is still1 unit. What is the width of each piece? 2. What is the size of the square in Step 3? Copy and complete:.1_ +.1_ by.1_ +.1_ 3. In Step 4, you divided 5 unit squares into 7 equal pieces. The length of each piece is still 1 unit. What is the width of each piece? 4. What is the size of the square in Step 4? Copy and complete:.1_ +.1_ by.1_ +.1_ 5. Use the side length you found in Exercise 2. Square the length to find the area of the square. You may need to write the mixed number as an improper fraction. Is this area greater than or less than 14? 6. Use the side length you found in Exercise 4. Square the length to find the area of the square. You may need to write the mixed number as an improper fraction. Is this area greater than or less than 14? 7. Use your answers in Exercises 5 and 6. Copy and complete the statement using overestimate or underestimate. Explain your reasoning. a. The side length of the square formed in Step 3 is an.1_ for Vi4. b. The side length of the square formed in Step 4 is an.1_ for Vi4. 8. Explain how you know that the actual value of Vi4 is between the side lengths you found in Exercise 2 and Exercise Give another mixed number as an approximation of Vi4. Choose a number between the values you found in Exercise 2 and Exercise 4. a. Check your approximation by squaring. b. Is your choice an overestimate or an underestimate for Vi4? c. Which do you think is the best approximation for Vi4: the length in Exercise 2, the length in Exercise 4, or your choice here in Exercise 9? Explain your reasoning. 7.2 Approximate Square Roots

11 Approximate Square Roots VOCABULARY and CONCEPTS An irrational number is a number that cannot be written as a quotient of two integers. The decimal form of an irrational number neither terminates nor repeats. The set of real numbers consists of all rational and irrational numbers. Every real number can be represented on the real number line. Irrational Numbers V3 is irrational because 3 is not a perfect square is irrational because it neither terminates nor repeats. EXAMPLE 1 Approximate Vi3 to the nearest integer. Make a list of integers that are perfect squares: 0, 1, 4, 9, 16, 25, < 13 < 16 V9 <Vi3 < v16 Identify perfect squares closest to 13. Take positive square root of each number. 3 < Vi3 < 4 Evaluate square roots. ~Answer The average of 3 and 4 is 3.5, and (3.5) 2 = Because 13 > 12.25, Vi3 is closer to 4 than to 3. So, Vi3 = 4. Practice for Example 1 Approximate the square root to the nearest integer. 1. ViO 2. Vi7 3. V2s 4. -'./66 EXAMPLE 2 Approximate Vi3 to the nearest tenth. You know from Example 1 that Vi3 is between 3 and 4. Make a list of squares of 3.1, 3.2,..., 3.9. From the list, you can see that 13 is between and So, Vi3 is between 3.6 and 3.7. ~Answer The average of 3.6 and 3.7 is 3.65, and (3.65) 2 = Because 13 < , Vi3 is closer to 3.6 than to 3.7. So, Vi3 = = = = = = = Chapter 7 Square Roots and the Pythagorean Theorem

12 Alg 2.0 Students understand and use such operations as taking the opposite, finding the reciprocal, taking a root, and raising to a fractional power. They understand and use the rules of exponents. 4 Practice for Example 2 Approximate the square root to the nearest tenth. 5. Vi9 6. v30 7. V8s 8. -Vli2 EXAMPLE 3 (4r~Vp41Atj ~Vnd Order~Atj Rud N~ers Order the numbers from least to greatest: ~' v'i6, - 2.2, -ill, Vs. Begin by graphing the numbers on a real number line. Approximate - ill and '16: -ill~ and V6 ~ Vi2-2.2 ~ Vs v'i6 I I I I I + I Read the numbers from left to right: -ill, - 2.2, ~ ' '16, Vl6. Practice for Example 3 9. Order the following numbers from least to greatest: ViO, - ~, - Vs, -2, 1.3 EXAMPLE 4 F~Utj tv D~st~.... When you are at a height h, the distance d to the horizon can be approximated using the equation d = 3.5Tf h. The distance d is measured in kilometers and the height h is measured in meters. Approximate the distance to the horizon if you are at the top of a lighthouse that is 52 meters high. d = 3.57Vh = 3.57ill = 3.57(7.2) = Write formula. Substitute 52 for h. To the nearest tenth, V52 = 7.2. Multiply. ~Answer The distance to the horizon is about 26 kilometers. Practice for Example Use the formula in Example 4. Find the approximate distance to the horizon if you are at the top of a building that is 77 meters high. 7.2 Approxi mate Square Roots

13 Pract1ce Extra Practice p. 504 Identify the two integers closest to the number. 1. rn 2. m 3. - v Vi9 Approximate the square root to the nearest integer. 5. Vs 6. Vi9 7. -m 9. -V Vil 11. V m 14. Vs vl41 Approximate the square root to the nearest tenth. 17. V3 18. V Vil 21. V V Vi42 8. m 12. V m 20. v' V2iO Order the numbers from least to greatest. 25. \164, -5, V9, V3, 5.5, -v16, ~ V4, -3.6, - Vl 28. -V6, % 7, You buy 134 square feet of linoleum to cover the floor in a square kitchen. There are 8 square feet of linoleum left over. Approximate the side length of the kitchen to the nearest foot. 30. You are using railroad ties to build a square flower bed like the one shown. You want to place a railroad tie on the diagonal to form two triangular beds. Find the length of the diagonal by using the expression V2J. where s is the side length of the flower bed. Round your answer to the nearest tenth. 31. Computer screens are measured according to their diagonal length. The diagonal length of a computer screen is Y2362 centimeters. Approximate the diagonal length to the nearest tenth. REASONING The Venn diagram shows the relationships among various sets of numbers. Copy the diagram and place the given number in the appropriate part of the diagram. Then list all sets to which the given number belongs V An animal's maximum walking speed s_{in feet per second) can be calculated using the formulas = 5.66Y. where. is the animal's leg length (in feet). What is the maximum walking speed for an elephant with a leg length of 8 feet? f ft Irrational numbers Chapter 7 Square Roots and the Pythagorean Theorem

14 Tutor classzone.com Approximate the square root to the nearest integer. 1. Vi5 2. -v48 3. m 5. -m 6. Vi Vs3 9. V ill 11. v' Vi40 8. m 12. -V2il FIND THE ERROR Describe and correct the error in approximating the square root to the nearest integer. 13. v3e ' 14. V19 39 f alls between 36 and 49. Because 39 is closer to 36, X 19 falls between 16 and 25. Because 19 is closer to 25, v3e = 36. V19 = v'25 = 5. x' Approximate the square root to the nearest tenth. 15. V / V vuo 20. V ~ 18. vtio 22. vt89 Order the numbers from least to greatest , Vs3, -8, v'21, -~,-4.7, -% 24. %4, 8.2, vl37, , v'4.8, V8.61, An A1 sheet of paper has a width of 594 millimeters. The length of an A1 sheet of paper is Y2 times its width. Approximate the length of an A1 sheet of paper to the nearest millimeter. 28. The maximum speed s (in knots, or nautical miles per hour) for a sailboat using wind power can be found using the formula s = 1.34Yl where. is the length of the boat's waterline (in feet). What is the maximum speed of a 34 foot sailboat to the nearest knot? 29. The radius r of a circle with area A is given by the formula r = ~ Find the radius of a circle that has an area of 31.4 square centimeters. Use 3.14 for 'TT. Round your answer to the nearest tenth. REASONING Tell whether the number is rational or irrational. Explain. 2 3o. V o m 11 REASONING Give an example of the real number being described. 34. Integer 36. Irrational number in square root form 35. Rational number that is not an integer 37. Irrational number in decimal form 7.2 Approximate Square Roots

15 Mid-Chapter Review VOCABULARY square root, p. 288 irrational number, p. 294 perfect square, p. 288 real numbers, p. 294 Vocabulary Exercises 1. Copy and complete: A _1_ of a real number a is a real number b such that b 2 = a. 2. Give three examples of irrational numbers. 3. Give three examples of numbers that are perfect squares. Fifu;l S1ua,r~ Roots of Pe.rfeut S1ua,ru PP EXAMPLE Evaluate the expression. a. VlOO = 10 The positive square root of 100 is 10. b. -1/25 = - 5 The negative square root of 25 is -5. c. ±\149 = ±7 The positive and negative square roots of 49 are 7 and -7. Evaluate the expression. 4. V v' V9 8. ±v' :±:%4 9. Vs41 Aff'Yoxiut,al;~ S1ua,r~ Roots PP EXAMPLE Approximate Y7 to the nearest integer. Make a list of integers that are perfect squares: 0, 1, 4, 9,.... Identify the perfect squares closest to 7. Take the positive square root of each number. 2 < Y7 < 3 Evaluate the square roots. Because 7 is closer to 9 than to 4, Y7 is closer to V9 = 3. So, to the nearest integer, Y7 = 3. Approximate the square root to the nearest integer. 10. m 11. V V Vs5 12. m 15. -Vli9 Chapter 7 Square Roots and the Pyt hagorean Theorem

16 Mid-Chapter Test Find the two square roots of the number Evaluate the expression. 9. V v' ±m 14. -\1' Vsl 18. ±V ±% Vi vl V1 16. ±Y ±ViOO Approximate the square root to the nearest integer. 21. Vs 22. v' V V Vi Vs v V Vi73 Approximate the square root to the nearest tenth. 33. V2 34. v V V % V Vi v'lli 43. V V V V vm 40. -Vs V262 Order the numbers from least to greatest Vs, ~ 4.7, V6 46. Vs, -7, ~' v'3, 2~, -Vi4, m, 1 i, V5, A school has an athletic practice field in the shape of a square with an area of 10,000 square feet. Find the side length of the field. 50. Jerome is designing a flower garden. He wants the garden to be square and to be bordered by a decorative fence. The garden will have an area of 64 square feet. How many feet of fence does Jerome need? 51. A stained-glass window is in the shape of a square with an area of 2304 square inches. What is the perimeter of the window? 52. You buy a bag of grass seed that covers an area of 650 square meters. You spread the entire bag over an area in the shape of a square. Find the side length of the square to the nearest tenth. 53. A person's maximum running speeds (in meters per second) can be approximated using the formulas = Vi:6 where. is the person's leg length in meters. Find the maximum running speed of a person with a leg length of 0.75 meter. Round your answer to the nearest tenth. Chapter 7 Mid-Chapter Test

17 0 Investigating Right Triangles Goal Examine the relationship among the lengths of the sides of a right triangle. Materials graph paper scissors Q.UESTION How are the lengths of the sides of a right triangle related to each other? A right triangle has one right angle (90 ) and three sides. The side opposite the right angle is called the hypotenuse. The two sides that form the right angle are called the legs. leg leg EXPLORE 1 Draw a right triangle with legs of length 3 units and 4 units on graph paper. For each leg, draw a square that has a leg as one side. What is the sum of the areas of these two squares?!"'- 3 4? ~ Measure the hypotenuse using graph paper. If you draw a square with the hypotenuse as one side, what is its area? Compare the sum of the areas you found in Step 1 with the area you found in Step 2. What do you notice? Draw Conclusions Repeat Steps 1-3 for right triangles with legs of the given lengths. 1. 5, , , Let the lengths of the legs of a right triangle be a and b, and let the length of the hypotenuse be c. Make a conjecture about the relationship between the lengths of the legs and the length of the hypotenuse.

18 ~( Gr. 7 MG 3.3 Know and understand the Pythagorean theorem and its converse "'I ~ and use it to find the length of the missing side of a right triangle and the lengths of other line segments and, in some situations, empirically verify the Pythagorean theorem by direct measurement. EXPLORE 2 Make right triangles. Cut a right triangle out of graph paper. Make three copies of it. Arrange the right triangles to form a square within a square, as shown. Draw Conclusions 5. How is the area of the inner square related to the area of the outer square? In Exercises 6-9, let a, b, and c be the lengths of the sides of a right triangle with a < b < c, as shown. 6. Write an expression for the area of one of the triangles in terms of a and b. 7. Write an expression for the area of the outer square in terms of c. 8. Explain why the length of each side of the inner square is b - a. 9. A way to write the area of the inner square is (b - a) (b - a), or b 2-2ab + a 2 once you use the distributive property to find the product. Use the relationships you have determined in Exercises 5-8 to create a formula that relates a, b, and c. Copy and complete the steps. c 2 = (_1_) ( ~ab ) + (b 2-2ab + a 2 ) = _]_ + b 2-2ab + a 2 =_]_+_]_ Simplify by combining like terms to write the formu la. 7.3 Use the Pythagorean Theorem

19 Use the Pythagorean Theorem VOCABULARY and CONCEPTS A ri~:ht trian~:ie is a triangle with one right angle. In a right triangle, the side opposite the right angle is the hypotenuse. hy/yd leg The two sides that form the right angle leg in a right triangle are the Ie~:s. When a statement is written in if-then form, the if part contains the hypothesis and the then part contains the conclusion. Pythagorean Theorem If a triangle is a right triangle, then the sum of ~ the squares of the lengths of the legs equals b c the square of the length of the hypotenuse. Algebra For the right triangle shown, a2 + b2 = c2. a EXAMPLE 1 W r ~t~ftj Ij- ThA!,f'V S t P..~te,/111./e,tVtr Write each statement in if-then form and identify the hypothesis and conclusion. a. The longest side in a right triangle is the hypotenuse. ~Answer If a side of a right triangle is the longest side, then it is the hypotenuse. Hypothesis: a side of a right triangle is the longest side Conclusion: the side is the hypotenuse b. Negative numbers are less than zero. ~Answer If a number is negative, then it is less than zero. Hypothesis: a number is negative Conclusion: the number is less than zero Practice for Example 1 Write the statement in if-then form. 1. Even numbers are divisible by All integers are rational numbers. 3. Identify the hypothesis and the conclusion in the statement of the Pythagorean theorem. Chapter 7 Square Roots and the Pythagorean Theorem

20 ~Ill... Gr. 7 MG 3.3 Know and understand the Pythagorean theorem and its converse ~ and use it to find the length of the missing side of a right triangle and the lengths of other line segments and, in some situations, empirically verify the Pythagorean theorem by direct measurement. EXAMPLE 2 For the right triangle shown, find the length of the hypotenuse. a2 + b2 = c = c = c = c 2 ±V960 = c 30 = c Pythagorean theorem Substitute 18 for a and 24 for b. Evaluate powers. Add. Definition of square root ~ cern 18em~ 24em Choose positive square root; length is nonnegative. ~Answer The length of the hypotenuse is 30 centimeters. EXAMPLE 3 A rectangular table measures 72 inches by 36 inches. What is the length of the diagonal from one corner of the table to the opposite corner? Round your answer to the nearest tenth of an inch. Solution The diagonal divides the rectangle into two identical right triangles. Find the length of the hypotenuse of either triangle. a2 + b2 = c = c = c 2 Pythagorean theorem Substitute 72 for a and 36 for b. Simplify. Y6480 = c Definition of square root 80.5 = c Approximate square root. ~Answer The diagonal of the table is about 80.5 inches long. 4.n m s. Practice for Examples 2 and 3 Find the length of the hypotenuse. 20m;v- 21 mi cmm 6. ~ cern 21 e m~ 28 em 7. A television screen is measured by the length of its diagonals. A rectangular television screen is 9 inches wide and 12 inches long. What is the length of its diagonal? 7.3 Use the Pythagorean Theorem

21 Pract1ce Extra Practice p. 504 Write the statement in if-then form and identify the hypothesis and the conclusion. 1. A glass that is ~ full is 60% full. 2. x = 2.3 and y = 1.2, so xy = a= -4, so a 2 = FIND THE ERROR Describe and correct the error in finding the length of the hypotenuse. 5ft~ 8ft c 2 = a 2 + l:l c 2 = c 2 = 13 c=m c = 3.6 lhe length of the hypotenuse is about 3.6 feet. Let a and b represent the lengths of the legs of a right triangle. Find the length c of the hypotenuse. Round to the nearest tenth if necessary b = 3 7. a=5 a~!~ b =4 X b=3, 8. a= 6, b = 4 9. a= 3, b = a= 5, b = a= 9, b = a= 5, b = a= 4, b = 8 Find the length c of the hypotenuse. Round to the nearest tenth if necessary ~ cin. 1n.~ 8 in. 15. cmm~ ~ 3mm 6mm 17. The Greens have a rectangular pool that is 23 feet long and 20 feet wide. Find the length of a diagonal of the pool to the nearest tenth. 18. A tree is 16 feet tall and casts a shadow 24 feet long. Find the distance between the top of the tree and the tip of the tree's shadow to the nearest foot. 19. REASONING What happens to the length of the hypotenuse of a right triangle when you double the lengths of the legs? Give an example to support your conclusion. f ft eft Chapter 7 Square Roots and the Pythagorean Theorem

22 Tutor classzone.com Write the statement in if-then form and identify the hypothesis and the conclusion. 1. A fish tank that is 80% full is ~ full. 2. X = 2 + 5, SO X = a = 0, so a 2 = FIND THE ERROR Describe and correct the error in finding the length of the hypotenuse. c2 = c 2 = c = 145 The length of the hypotenuse is 145 meters. X, Let a and b represent the lengths of the legs of a right triangle. Find the length c of the hypotenuse. Round to the nearest tenth if necessary. 5. a= 1, b = 5 6. a= 8, b = 4 7. a= 6, b = 6 8. a= 4, b = a= 2, b = a= 10, b = a= 30, b = a= 15, b = a= 11, b = You are trying to determine the distance across a pond. You put posts into the ground at points A, B, and C so that angle B is a right angle. You measure and find that the distance AB is 18 feet and the distance CB is 28 feet. How wide is the pond from A to C? Round your answer to the nearest foot. 15. Drywall comes in 4 feet by 8 feet sheets. To get the sheets of drywall through a small window of an upper-level apartment, the workers must pass the sheets diagonally through the window. The window is a rectangle that is 3 feet wide and 4 feet tall. Will the workers be able to pass the drywall through the window? Explain. 16. To find the length of segment AB shown, draw dashed line segments to form a right triangle with segment AB as the hypotenuse. Then follow these steps: a. Count grid squares to find the lengths of the legs of the right triangle. b. Use the Pythagorean theorem to find the length of the segment to the nearest tenth. A / / I I v T v I B 17. REASONING What happens to the length of the hypotenuse in a right triangle when you make the lengths of the legs half of their original lengths? Give an example to support your conclusion. 7.3 Use the Pythagorean Theorem

23 ' E lor Investigating Sides and Angles of Triangles Goal Examine the relationship between the lengths of the sides of a triangle and the measures of the angles of the triangle. Materials graph paper scissors colored pencils Q.UESTION EXPLORE 1 How can you use the side lengths of a triangle to decide whether it is a right triangle? Ba-Ud a- r01vt tr~~t~ Cut out strips of graph paper as follows. Cut 3 strips that are 3 units long. Cut 1 strip that is 5 units long. Cut 4 strips that are 4 units long. Cut 1 strip that is 6 units long. Shade one long edge of each strip in red. Place a 4 unit strip next to a 3 unit strip as shown to form a corner of a triangle. Take another 4 unit strip and form a corner at the other end of the 3 unit strip. Move the strips so that they form a triangle with side lengths 3, 4, and 4. Repeat Steps 3 and 4 with other strips to form a triangle with side lengths 3, 4, and 5 and a triangle with side lengths 3, 4, and 6. Take the corner of a piece of paper and lay it against each corner of each triangle. The piece of paper is a rectangle and so has right angles at its corners. Which of the triangles has a right angle at one of its corners?

24 ~... Gr. 7 MG 3.3 Know and understand the Pythagorean theorem and its converse ~ and use it to find the length of the missing side of a right triangle and the lengths of other line segments and, in some situations, empirically verify the Pythagorean theorem by direct measurement. Draw Conclusions 1. Consider the triangle you chose in Step 6 of Explore L Show that the side lengths of that triangle satisfy the relationship a 2 + b 2 = c 2 where a, b, and care the side lengths with c being the length of the longest side. 2. Copy and complete this conjecture: If the side lengths a, b, and c of a triangle satisfy the relationship a 2 + b 2 = c 2, then the triangle must be a.1_ triangle. EXPLORE 2 F ia1ai P y t9 or e,a;ft; tr ijyks A Pythagorean triple is a set of three positive integers a, b, and c such that a 2 + b 2 = c 2. The numbers 3, 4, and 5 form a Pythagorean triple. In Explore 1, you showed that a triangle with side lengths 3, 4, and 5 is a right triangle. You can find other Pythagorean triples and show that they also form right triangles. Choose any two positive integers m and n such that m < n. Use formulas to generate a Pythagorean triple. Use your values form and n to find a, b, and c as follows : a = n 2 - m 2 b = 2mn Show that a 2 + b 2 = c 2 is true for the numbers you generated. That is, show that they form a Pythagorean triple. Draw Conclusions 3. Use the Pythagorean triple a, b, and c you found in Explore 2. a. Use the method from Explore 1, Steps 1-4, to create a triangle with side lengths a, b, and c. b. Use Step 6 of Explore 1 to show that the triangle you created is a right triangle. 4. Use the formulas in Explore 2 to generate two more Pythagorean triples. 5. If the numbers a, b, and c form a Pythagorean triple, what do you expect is true about 2a, 2b, and 2c? Give an example to test your conjecture.. -1\\i~-.. "-: J ~; ;."!"' -~ Use the Converse of the Pythagorean Theorem

25 Use the Converse of the Pythagorean Theorem VOCABULARY and CONCEPTS The converse of a statement written in if-then form is formed by switching the hypothesis and conclusion of the statement. The converse of a true statement is not necessarily true. In the case of the Pythagorean theorem, the converse is true. Converse of the Pythagorean Theorem If the sum of the squares of the lengths of ~ two sides of a triangle equals the square b c of the length of the third (longest) side, then the triangle is a right triangle. a Algebra For the triangle shown, if a 2 + b 2 = c 2, then the triangle is a right triangle. EXAMPLE 1 ~r~t~ Con/~ers~s Write the converse of the if-then statement. Tell whether the converse is true or false. a. If you are a guitar player, then you are a musician. ~Answer If you are a musician, then you are a guitar player. False. A violinist who does not play the guitar is still a musician. b. If x is odd, then 3x is odd. ~Answer If 3x is odd, then x is odd. True. If the product of two numbers is odd and one of the numbers is odd, then the other number must be odd. EXAMPLE 2 lruh/tify ~ ~ Rij kt TrU'vltj k.... Use the converse of the Pythagorean theorem to determine whether a triangle with side lengths a = 5, b = 12, and c = 13 is a right triangle. Solution a 2 + b 2 :1:. c 2 Converse of Pythagorean theorem :1: Substitute 5 for a, 12 for b, and 13 for c :1:. 169 Evaluate powers. 169 = 169./ Add. ~Answer The triangle is a right triangle. Chapter 7 Square Roots and the Pythagorean Theorem

26 ~ ~ Gr. 7 MG 3.3 Know and understand the Pythagorean theorem and its converse and use it to find the length of the missing side of a right triangle and the lengths of other line segments and, in some situations, empirically verify the Pythagorean theorem by direct measurement. EXAMPLE 3 Show that a triangle with sides of length 6 inches, 10 inches, and 12 inches is not a right triangle. The length of the longest side is 12 inches, so let c = 12. a2 + b2 J: c J: =I= 144 Converse of Pythagorean theorem Substitute 6 for a, 1 0 forb, and 12 for c. Evaluate powers and add. ~Answer The triangle is not a right triangle, because together the Pythagorean theorem and its converse say that only right triangles satisfy a 2 + b 2 = c 2. Practice for Examples 1, 2, and 3 1. Write the converse of this statement: If n is an even number, then 2n is an even number. Tell whether the converse is true or false. If it is false, explain why. Determine whether the triangle with the given side lengths is a right triangle. 2. 7,24, ,20, ,5, V34 EXAMPLE 4 Ve-rify ~11/j a, Rijlvt Tr i-tvyvj te- A door is braced with a diagonal crosspiece. Are the identical triangles formed in the door right triangles? Explain. Use the converse of the Pythagorean theorem. t em a2 + b2 J: c J: Converse of Pythagorean theorem Substitute 132 for a, 224 for b, and 260forc. em 67,600 = 67,600./ Evaluate powers and add. ~Answer Yes, the diagonal crosspiece and the sides of the door form two right triangles because the given lengths satisfy the converse of the Pythagorean theorem.... Practice for Example A rectangular picture frame is 15 inches wide and 36 inches long. On the back, there is a 39 inch diagonal crosspiece for support. Are the triangles formed in the frame right triangles? Explain. 7.4 Use the Converse of the Pythagorean Theorem

27 Pract1ce Extra Practice p. 504 Write the converse of the if-then statement. Tell whether the converse is true or false. If it is false, explain why. 1. If you are a soccer player, then you are an athlete. 2. If a number is negative, then the number is less than zero. 3. If an animal is a whale, then the animal is a mammal. 4. If a...;- 4 = 3, then a...;- 3 = 4. Determine whether the triangle with the given side lengths is a right triangle. 5. a= 35, b = 21, c = a= 20,b = 21, c = a = 1.44, b = 0.36, c = a = 9.2, b = 3.4, c = a = 39, b = 52, c = a = 16, b = 24, c = a = 3.6, b = 4.8, c = a= 45, b = 108, c = 117 Tell whether the triangle is a right triangle ~20 ~~ 14.~ Determine whether the triangle with the given side lengths is a right triangle , v'lu, , 9, , 3.5, , V225, , 2, v' , Vi%, A sail has the shape of a triangle. The lengths of the sides are 146 inches, 131 inches, and 84 inches. Is the sail a right triangle? Explain. 23. Nicole is making a picture frame that is 12 inches long by 10 inches wide. She measures and finds that the length of a diagonal is 16 inches. Are the angles opposite the diagonal right angles? Explain. 24. A rectangular banner is 2.5 feet wide and 6 feet long. The banner has a diagonal line 6.5 feet long that separates the banner into two triangles. Can you tell from the given lengths whether the triangles formed in the banner are right triangles? Explain. 25. REASONING A worker builds a wooden frame to hold wet cement while it dries. The frame appears to be a rectangle. Explain how the worker can use a tape measure to know for sure that the corners of the frame are right angles. Chapter 7 Square Roots and the Pythagorean Theorem

28 Tutor classzone.com Write the converse of the if-then statement. Tell whether the converse is true or false. If it is false, explain why. 1. If an animal is a lizard, then the animal is a reptile. 2. lfx = 1, then.xy = y. 3. If it is snowing, * then the temperature is below freezing. 4. If 12 + = 16, then 12 X ~ = 16. Determine whether the triangle with the given side lengths is a right triangle. 5. a= 24, b = 10, c = a= 34, b = 44, c = a = 17, b = 23, c = a = 0.36, b = 0.48, c = a = 7.56, b = 8.49, c = a = 54, b = 72, c = a = 1.27, b = 3.46, c = a= 228,b = 95,c = 247 Tell whether the triangle is a right triangle ~16 ~~ ~75 ~~ Determine whether the triangle with the given side lengths is a right triangle , v%1, , V289, , 2.6, vm, 13, Show that a triangle with sides of length 8 inches, 9 inches, and 13 inches is not a right triangle. 18. V122s,28, , 3.2, Each wilderness troop at a camping outing has created its own flag. Your troop's flag is triangular with side lengths of 15 inches, 18 inches, and 23 inches. Is the flag a right triangle? Explain. 24. You are building a tool shed. The framing for the floor measures 12 feet by 7 feet. To ensure the floor is "square," you measure the diagonal and find it to be 15 feet long. (Carpenters consider the framing to be "square" when the angles measure 90.) Does the framing form a rectangle? Explain. 25. REASONING Explain the difference between the Pythagorean theorem and the converse of the Pythagorean theorem. Give an example to show how each is used. 12ft 7ft 7.4 Use the Converse of the Pythagorean Theorem

29 Problem Solving and Reasoning Problem A square has a side length of 4 inches. The midpoints of the sides of the square are connected to form a square within the original square. The midpoints of this square are then connected to form a third square. How is the side length of the innermost square related to the side length of the original square? Suppose this procedure is repeated using the innermost square as the starting square. Predict the side length of the new innermost square. Use a diagram Solution to explain mathematical 0 Draw the three squares as described in Ia 2 in. reasoning as part of the problem. Label the side length of the MR2.5. ~ outermost square as 4 inches. Each side of the second square is the hypotenuse of a right 4 in. triangle with legs of length 2 inches. e 1 Find the the side length X of the second Make precise calculations as part square. Use the Pythagorean theorem.?~.~~~:~ ~ x2 = x 2 =4+4 x 2 = 8 x = Vs inches E) Find the side length y of the third square. Each side of the third square is the hypotenuse of a right triangle with legs of length ~' or V,f inches. Use the Pythagorean theorem to find y. i = (VfY + (VfY y = i = 4 y = 2 inches Develop generalizations of the results obtained as part of MR 3.3. ~ Predict the side length of the new innermost square by generalizing the relationship between the side lengths. The side length of the innermost square, 2 inches, is half the side length of the original square, 4 inches. If the procedure were repeated using the innermost square as the starting square, the new innermost square would have a side length that is half of 2 inches, or 1 inch. Chapter 7 Square Roots and the Pythagorean Theorem

30 Practice 1. Semicircles with areas A, B, and C are constructed on the sides of a right triangle as shown. Make and test a conjecture about the relationship between A + B and C. MR 2.4, MR An approximately square region with an area of about 256 square miles is being sprayed with pesticide to reduce the mosquito population. Suppose the center of town A is in the spray zone. If the center of town B is 20 miles from the center of town A, is it possible for the center of town B to be in the spray zone? Explain. MR 2.5, MR Using the number line shown below, estimate a number between rn and m. Then actually find a number between ffi and v'l2 without using a calculator. Explain your reasoning. MR 2.3, MR 2.5 v'uv12 I I I I, A painter needs a ladder to reach from a point on the ground 7 feet from the base of a house to a height of 23 feet on the house. The painter's ladder is able to extend from 14 feet to 25 feet. MR 2.1, MR 2.7 a. To the nearest foot, calculate the length the ladder needs to be extended. Can the painter use the ladder? Explain why it is not necessary to find an exact distance. b. Use estimation to check that your answer to part (a) is reasonable. 5. A 30 foot tall utility pole stands between a sidewalk and a street. A guy wire connects the top of the pole to the ground to increase the stability of the pole. The wire runs through the end of a bar extended from the pole as shown to protect people on the sidewalk. MR 1.3, MR 2.4 T 12ft 1 a. How much wire is used? I 30ft 1 b. If the bar were lowered, would the amount of wire used increase, decrease, or stay the same? Explain your reasoning. 6. Write a formula for the perimeter P of a square in terms of its area A. If a square has an area equal in value to its perimeter, what is the side length of the square? Explain how you found your answer. MR 1.1, MR Tim wants to build a skateboard ramp that is 100 centimeters long and 28 centimeters high. The base and height of the ramp must form a right angle. MR 2.5, MR cm~ ~ base a. Explain why the base of the ramp cannot be 90 centimeters long. b. How long should Tim make the base of the ramp? Explain your reasoning. (Hint: Use your answer to part (a) as a starting point.) Problem Solving and Reasoning

31 Leap Frog Complete the exercises below to find the path the frog takes to get to the rock. Each answer can be found on a lily pad along with a letter. Copy the letter onto your paper to answer this question: What was the nationality of Pythagoras? Evaluate the expression. 1. VI% 2. - V16 3. Y What is the side length of a square with area 17 square units? 6. Evaluate Vx+4 when x = 32. Find the value of the variable. Round to the nearest whole number if necessary. 7. ""X 3~ 4 8. X~ /~ The lengths of the sides of a triangle are 5, 12, and c with c being the greatest length. What value of c is needed for the triangle to be a right triangle? 72 9.~ 11 v 2 Chapter 7 Square Roots and the Pythagorean Theorem

32 Chapter Summary and Tutor classzone.com VOCABULARY square root, p. 288 real numbers, p. 294 legs, p. 302 perfect square, p. 288 right triangle, p. 302 if-then form, p. 302 irrational number, p. 294 hypotenuse, p. 302 converse, p. 308 Vocabulary Exercises 1. Copy and complete: The set of.1_ consists of all rational and irrational numbers. 2. Copy and complete: The.1_ of a statement written in if-then form is formed by switching the hypothesis and conclusion of the statement. Fiful s1uare- Root! of PerfU/t s1uaru pp.2ss-291 A square root of a real number a is a real number b such that b 2 = a. EXAMPLE a. b. -vloo = -10 c. :±:%4 = ±8 The positive square root of 36 is 6. The negative square root of 1 00 is The positive and negative square roots of 64 are 8 and -8. Evaluate the expression. 3. Vfi v'49 5. ±v ~ 8. ±v'i21 9. v' V1 10. v'361 Al?f'Yoxiutai:e- s1uare- Root! PP EXAMPLE Approximate Y24 to the nearest integer. Make a list of integers that are perfect squares: 0, 1, 4, 9, 25, < 24 < 25 Identify perfect squares closest to 24. v16 < v'24 < V25 Take positive square root of each number. 4 < v'24 < 5 Evaluate square roots. The average of 4 and 5 is 4.5, and (4.5) 2 = Because 24 > 20.25, v'24 is closer to 5 than to 4. So, v'24 = 5. Approximate the square root to the nearest integer. 11. v'8 12. v5o Vi V V Vi m 18. Vi50 Chapter Summary and Review

33 Chapter Summary and Review Uu the Pytlt..a:Jorea~t Ifteore-m PP When a statement is written in if-then form, the if part contains the hypothesis and the then part contains the conclusion. EXAMPLE Write the following statement in if-then form and identify the hypothesis and conclusion: A square is a figure with four sides. ~Answer If a figure is a square, then it has four sides. Hypothesis: a figure is a square Conclusion: the figure has four sides PYTHAGOREAN THEOREM If a triangle is a right triangle, then the sum of the squares of the lengths of the legs equals the square of the length of the hypotenuse. b~ For the right triangle shown, a 2 + b 2 = c 2. EXAMPLE a2 + b2 = c = c = c = c 2 ±~=c Find the length of the hypotenuse. Pythagorean theorem Substitute 15 for a and 16 for b. Evaluate powers. Add. Definition of square root a 15~ 21.9 = c Choose positive square root; length is nonnegative. Write the statement in if-then form. Identify the hypothesis and conclusion. 19. The length of either leg of a right triangle is less than the length of the hypotenuse. 20. An integer whose last digit is 0 is divisible by The hypotenuse of a right triangle is opposite the right angle. Find the length of the hypotenuse. Round to the nearest tenth if necessary em ~ 20cm mi Chapter 7 Square Roots and the Pythagorean Theorem 17ft

34 @Home Tutor classzone.com The converse of a statement written in if-then form is formed by switching the hypothesis and conclusion of the statement. The converse of a true statement is not necessarily true. EXAMPLE Write the converse of the following if-then statement: If x = 3, then x2 = 9. Tell whether the converse is true or false. ~Answer If x 2 = 9, then x = 3. False. Another possible value of xis -3. CONVERSE OF THE PYTHAGOREAN THEOREM If the sum of the squares of the lengths of two sides of a triangle equals the square of the length of the third (longest) side, then the triangle is a right triangle. For the triangle shown, if a 2 + b 2 = c 2, then the triangle is a right triangle. b~ a EXAMPLE a2 + b2 :1 c2 Show that a triangle with sides of length 28, 45, and 53 is a right triangle : Converse of Pythagorean theorem Substitute 28 for a, 45 for b, 53 for c : Evaluate powers = 2809v" Add. ~Answer The triangle is a right triangle. 45 Write the converse of the if-then statement. Tell whether the converse is true or false. If it is false, explain why. 25. If x is an even number, then x + 1 is an odd number. 26. If an integer is divisible by 2, then it is even. 27. If x is greater than 4, then x is greater than For positive numbers a and b, if a and bare both less than 1, then ab is less than 1. Determine whether the triangle with the given side lengths is a right triangle , 20, , 7, , 72, , 42, 47 Chapter Summary and Review

35 Chapter Test Evaluate the expression. 1. V Vsl 3. ±vm 4. Yo 5. -Vi69 6. ±VI 7. -V ±V2s6 Approximate the square root to the nearest integer. 9. ViO 10. V V ' vti m 15. v'i Vi61 Order the numbers from least to greatest. 17. V2, 1.2, 1 5 2, -1.9, -~. -V , t Vs, -2.9, - V2o, -~ Write the statement in if-then form and identify the hypothesis and conclusion. 19. A rational number in decimal form is a terminating decimal. 20. An irrational number is a real number. For the right triangle shown, find the length of the hypotenuse. Round to the nearest tenth if necessary. 21. ~ c 30~ Write the converse of each if-then statement. Tell whether the converse is true or false. If it is false, explain why. 24. If you are adding two negative integers, then the sum is negative. 25. If a number is an integer, then it is rational. ~ 24 ' - Determine whether the triangle with the given side lengths is a right triangle , 15, , 18, ,16, v'9, 5, ,40, , Vi6, Refer to the diagram of a ladder leaning against a chimney. How long is the ladder? 35. A ramp is extended from the back of a truck to help workers unload a refrigerator. The ramp touches the ground at a point 8 feet behind the truck. The height from the top of the ramp to the ground is 4 feet. How long is the ramp? Round your answer to the nearest tenth ,56, o, 27, vm Chapter 7 Square Roots and the Pythagorean Theorem

36 Multiple Choice Chapter Test What is the value of - Vi6? -4 ±256 Which integer is a perfect square? 7. What is the if-then form of the statement "A polygon that has three sides is a triangle"? If a polygon is a triangle, then it has three 11 If a triangle has three sides, then it is a polygon. 100 If a polygon has three sides, then it is A square field has the area shown. a triangle. What length of fencing is If a polygon is not a triangle, then it around the field? does not have three sides. Area 8. What is the length of the hypotenuse in the 400m 2 20ft~ What is the value of v'40 to the nearest 6 21ft 20.5 ft 22ft What is the converse of the statement "If n is an even number, then 2n is even"? Which list of numbers is in order from least to greatest? -2, -~, -0.2, V2, 2 If n is not an even number, then 2n is not even. If n is an even number, then 2n is odd. -~, -0.38, -3.8, -38, ill If 2n is an even number, then n is even. -i, -0.4, -4, 1.4, -5, -15, 1-5, 1 0.5, Vs If 2n is not an even number, then n is not even. 10. Which of the following are the side lengths The equation t = 0.45Vh gives the time of a right triangle? t (in seconds) that an object falling from a = 9, b = 40, c = 41 a height of h meters takes to reach the ground. A golf ball is dropped from a a = 19, b = 40, c = 49 height of 20 meters. In about how many a= 10, b = 45, c =50 seconds does it reach the a = 15, b = 15, c = sec 2sec 20 sec Multiple Choice Chapter Test