Sherry Angel

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.

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.

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.

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.

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

http://www.amazon.com/Sir-Cumference-Great-Knight-Angleland/dp/157091169X/ref=pd_bbs_sr_2?ie=UTF8&s=books&qid=1202863195&sr=-2

Picture- Amazon.com Circle graphics and info from slides-

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