1. 10-1 Circles Page 697

2. A circle is the set of all points in a plane that are a given distance from a given point in that plane. The given point is the center of the circle.

3. Radius A radius of a circle is a segment that has one endpoint at the center of the circle and the other endpoint on the circle.

4. Chord A chord of a circle is a segment that has its endpoints on the circle

5. Diameter A diameter of a circle is a chord that contains the center of the circle. A diameter is twice as long as a radius, or a radius is half as long as a diameter.

6. Pi Pi is an irrational number that is the ratio of the circumference of a circle to its diameter. Л = 22/7 or 3.14

7. Circumference The circumference of a circle is the distance around the circle. C = 2лr C = dл

8. Example 1 Refer to the application at the beginning of the lesson. The surveyor’s wheel has a diameter of 1.59 feet. What is the length of each spoke of the wheel?

9. Example 2 Find the circumference of a circle with a radius of 6.8 centimeters.

10. Example 3 In 1966, inspectors checked the accuracy of the Olympic marathon course by using the calibrated bicycle method. The inspectors rode bicycles equipped with counters that tracked the turns of the wheels. If the radius of a bicycle wheel is 13 inches and the counter shows 20,000 revolutions at the end of a course, how long is the course.

11. C = 2лr = 2л13inches = 26л =81.64 20,300 x 81.64 = 1657292 inches 1657292/63360 = 26.1567 =26.2 miles

12. Example 4 Find the exact circumference of circle p. C 2 = a 2 + b 2 16 30

13. 6. Name two chords. 7. If AL = 9.4, find KD. 8. Is NO < AL? Explain. 9. r = 7 d = ____ c = ____ 10. c = 76.4 d = _____ r = ______

14. Find the circumference of circle T.

15. Assignment Page 449 Problems 14-31