Measuring a Circle Sherry Angel Circumference 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 l 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. l This value is approximately 3. 14159265358979323846. . . We use Pi to represent this value.

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.

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.

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

A great book to read about Circumference, radius, and diameter. http: //www. amazon. com/Sir-Cumference-Great-Knight. Angleland/dp/157091169 X/ref=pd_bbs_sr_2? ie=UTF 8&s=books&qid=12028 63195&sr=-2

Credits Picture- Amazon. com Circle graphics and info from slidesstatic. bcsd. com/eissler_isp/gems/schneider. Ei s/Circumferenceof. Circle. ppt