9.6 Circles

Download 9.6 Circles

Post on 12-Jan-2015

909 views

Category:

Education

0 download

Embed Size (px)

DESCRIPTION

Chapter 9, Section 6: Circles

TRANSCRIPT

  • 1. Chapter 9 Section 6: Circles March 11, 2009

2. Find Circumference

  • ACircleis the set of all points that are the same distance from a given point.
  • The given point is theCENTERof the circle.
  • Circumference : the distance around the circle.

Center 3. Inside the Circle

  • Radius : a line segment that starts on the circle and ends at the center point.
  • Chord : segment whose end points are on the circle.
  • Diameter : a chord that passes through the center of the circle

4. Pi or

  • Pi or , pronounced pie, is the ratio of Circumference (or C) to Diameter (or d).
  • C = d
  • C/d =
  • Pi is constant =3.14159265358979323846
  • Pi as a fraction = 22/7
  • Because every circle is the same, the ratio is always the same, which is why pi is a constant.

5. Pi

  • C =d
  • If the d, or diameter, equals 1, then what is the Circumference (or C)?
  • C = (1), C =

6. Find the circumference of the circle with a diameter of 6ft.

  • C =dthe formula
  • C (approx.) = 3.14(6ft)Substitute
  • C = 18.84 Simplify!

6 Feet 7. Find the Circumference of Each Circle

  • Diameter = 200 miles
  • Radius = 30 millimeters
  • Diameter = 2.8 inches.

About 628 Miles About 188.4 mm About 8.8 inches 8. Making Circle (Pie) Graphs

  • A CENTRAL ANGLE is an angle whose vertex is the center of a circle.
  • There are 360 in a circle.
  • To make a Pie Graph, find the measure of each central angle by finding the proportion.

9. Use proportions to find the measures of the central angles.

  • Juans Weekly Budget :
  • Lunch (l) = 25%
  • Recreation (r) = 20%
  • Clothes (c) = 15%
  • Savings (s) = 40%

Find the percentage of 360 to find the degree measurement of the central angles. L = 90 R = 72 C = 54 S = 144 10. AT HOME

  • Use a cup opening or cap to make your circles if you dont have a compass.

11. Blood Types of Population

  • Tell me the degree measurements of the central angles if you were to make a Pie graph with this information.

43% 5% 12% 40% Type O Type AB Type B Type A 155 18 43 144 12. Students at Western High School: Find Central Angles.

  • Students at Western High School work in the following places; restaurants, 140; library, 15; auto shop, 60; retail stores, 75; and other places, 30. Round the measures of the central angles to the nearest degree.

Restaurant: 158 Retail: 84 Auto Shop: 68 Other: 34 Library: 17 13. Assignment #16:

  • Pages 472-473: 1-24. Skip #20.
  • Remember, if you need a circle and have no compass, then use a cup from home and trace the outside.