By now you should be able to explain the meaning of the following:

Transcription

1 Unit 4.7: Circles and Area Lesson: Drawing Circle Graphs Objectives: Students will review the vocabulary of circles. Students will learn to draw angles and measure angles. Students will learn to draw a circle graph using a percent circle, and then to draw a circle graph by calculation of angles. Materials Required: Measuring Angles Handout Percent Circle Compass Protractor Ruler Calculator Procedure: By now you should be able to explain the meaning of the following: Circle Radius Diameter We now need to add to that list a few new terms. Angle is the measure between two lines that share a vertex. Angles are named by their angles. Acute Obtuse Right Straight Reflex Angles are measured using a. Circles are drawn using a. Circles graphs are composed of which represent each quantity that is being graphed. 1

2 Measuring Angles To measure an angle place the crosshairs of the protractor on the vertex of the angle. Make sure that the zero line is in line with one line of the angle, and then counting from the zero, find the measure of the angle. We always measure to the nearest degree. Your teacher will review how to use a protractor on the smart board. Activity: Measure the following angles in the handout: Angle 1 2

3 Angle 2 Angle 3 3

4 Angle 4 Now that you know how to measure an angle, lets draw some. Activity On a blank piece of paper, draw the following angles. Then hand them to the person behind you to measure and correct. You are allowed to be 1 degree out. a) 40 degrees b) 88 degrees c) 160 degrees d) 200 degrees e) 300 degrees 4

5 Circle Graphs Using a Percent Circle Now that you are able to draw angles, we will be using two types of handouts to draw circle graphs. The first is called a percent circle. This is a circle that is pre-divided up into 100 percent. Each percent represents 3.6 degrees of the circle. To create a circle graph, calculate the percents of each sector and then using a ruler, draw in the appropriate sector sizes. Example: Eve is studying for his final exams. She set aside 8 hours to study. She studied 4 hours for math, 2.5 hours for LA, 2 hours for science and 1.5 hours for Social. Create a circle graph to show the amounts Eve studied. Calculate the percents studied for each subject. Math: Science: LA: Social: 5

6 On the circle graph, mark out the correct percentages using one of the lines as a starting point. 6

7 Normally we do not use a percent circle, so we have to be able to complete the circle graph by drawing our own angles. Example: Bob is wondering where all his money went so he created a simple circle graph of where he spends his money. Bob makes 600 dollars a month in his part time job, the following is a breakdown of where he spends it. Create a circle graph showing Bobs spending. Junk Food $200 Bike Payments $250 Clothes $50 Girlfriend $150 Calculate the percent of each sector, then use that percent to calculate the size of the sector knowing that a full circle is 360 degrees. (note that rounding sometimes makes the sectors a little off, so your total may not always be 360 degrees when you are done.) Junk Food: Bike Payments % 600 = Size of sector: Size of sector: 33 33% = 360 = 119 deg 100 Clothes: Girlfriend Size of sector: Size of sector: 7

8 Now using your compass and protractor, draw a circle and divide it up into 4 sectors labeled correctly. Students are to complete the following: Page 163#1,3,4,5 Homework Book Pages 97#1,3,5 Circle graphs can be drawn separately and placed into book with staple. 8