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People knew that the ratio between the circumference and the diameter of a circle is a constant for so long, that the original discoverer cannot be traced. The Babylonians found the first known value for Pi in around 2000 B.C.E. -They used (25/8).
The Bible uses a value of Pi equal to 3, which was most probably computed by measurement. Here is the verse from the old Testament, I Kings 7:23, where we read about the altar built inside the temple of Solomon: And he made a molten sea, ten cubits from one brim to the other: it was round all about, and his height was five cubits: and a line of thirty cubits did compass it about.
Another early source of pi traces back to Ancient Egypt, where the Rhind Papyrus was discovered in 1650 B.C.E. This Egyptian source doesn't explicitly state the value of Pi, but instead tells how to calculate the area of a circle as the square of eight-ninths of it's diameter.
In other words, Area = (8/9 d)2
pr2 = (8/9 x 2r)2
p= (16/9)2
Thus, according to the Rhind Papyrus, the value of pi is 3.16.
Archimedes (287? to 212B.C.E.) came up with the 1st theoretical calculation of Pi. He stated the following facts in his book: Measurement of the Circle .
1. A right triangle and a circle can have the same are if the two sides of the triangle making the right angle are equal to the radius and circumference of the circle
2. The ratio of the area of a circle to that of a square will be about 11:14 if the square has sides equal to the diameter of the circle. This is equal to saying that pi is about 22/7.
Area of the circle/ Area of the square = pr2 / 4r2 = 11/ 14
Hence, p = 4 x 11/14 or p = 22/7
3. The circumference of a circle is less than 3 and 1/7 times its diameter, but more than 3 10/71 times the diameter. In other words:
3 1/10D > Dp < 3 1/7 D
3 1/10D > Dp < 3 1/7 D
3 1/10 > p < 3 1/7
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