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Measuring a Circle

Measuring a Circle. Sherry Angel. Circumference. A circle is a shape with all points the same distance from the center. It is named by the center. The circle to the left is called circle A since the center is at point A. Circumference.

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Measuring a Circle

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  1. Measuring a Circle Sherry Angel

  2. Circumference • A circle is a shape with all points the same distance from the center. It is named by the center. • The circle to the left is called circle A since the center is at point A.

  3. Circumference • If you measure the distance around a circle and divide it by the distance across the circle through the center, you will always come close to a particular value, depending upon the accuracy of your measurement. • This value is approximately 3.14159265358979323846... We use Pi to represent this value.

  4. Circumference • The distance around a circle is called the circumference. The distance across a circle through the center is called the diameter. Pi is the ratio of the circumference of a circle to the diameter. Thus, for any circle, if you divide the circumference by the diameter, you get a value close to pi.

  5. Radius The radius of a circle is the distance from the center of a circle to any point on the circle. If you place two radii end-to-end in a circle, you would have the same length as one diameter. Thus, the diameter of a circle is twice as long as the radius. This relationship is expressed in the following formula: d = 2 ·r where d is the diameter and r is the radius.

  6. Summary • The number Pi is the ratio of the circumference of a circle to the diameter. • The value of Pi is approximately 3.14. • The diameter of a circle is twice the radius. Given the diameter or radius of a circle, we can find the circumference. • We can also find the diameter (and radius) of a circle given the circumference. • The formula for diameter is d = 2 · r • The formula for circumference is C = Pi · d

  7. A great book to read about Circumference, radius, and diameter. http://www.amazon.com/Sir-Cumference-Great-Knight-Angleland/dp/157091169X/ref=pd_bbs_sr_2?ie=UTF8&s=books&qid=1202863195&sr=-2

  8. Credits • Picture- Amazon.com • Circle graphics and info from slides-static.bcsd.com/eissler_isp/gems/schneiderEis/CircumferenceofCircle.ppt

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