What is Pi?Date: 4/1/96 at 7:14:46 From: Leigh Ausband Subject: Pi What is the significance of "pi"? Ashley Milburn Date: 4/2/96 at 4:51:41 From: Doctor Jodi Subject: Re: questions for Dr. Math: pi and finding pi Hi there! Pi is the ratio between the radius and circumference of a circle or between the radius and area of a circle. Mathematicians love pi because it's a transcedental number - its digits never end and never repeat. Archimedes had a neat way of approximating pi: To explain it you need to know a few words: inscribe, circumscribe, and polygon. If you inscribe a figure in a circle (place it inside a circle with only the vertices touching the circle) the figure will include some but not all of the area of the circle. Now if you circumscribe a circle with a figure (place the figure outside a circle with the vertices just touching the circle), the figure will include all of the area of the circle, plus a bit more. Archimedes used inscribed and circumscribed figures to approximate the area of the circle. (It's easiest with regular polygons like the equilateral triangle, square, regular pentagon, etc. - regular polygons have equal sides and equal angles. Do you know how to find their area? ) Then, knowing that the area of the circle is Pi*r ^2 (that's pi times radius squared), you can approximate pi. If you get a chance, try Archimedes' method and let us know what you find. -Doctor Jodi, The Math Forum Check out our web site! http://mathforum.org/dr.math/ |
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