Nobody because its a natural fact that the circumference of a circle divided by its diameter is always equal to pi.
Chat with our AI personalities
2*pi is one complete revolution, i.e. 360 degrees. Sin of 2*pi = sin 360º = 0
It's a Greek letter. Greek letters are often used to express constants (mathematical values that don't change).
Circumference of circle: 7.2*pi units or 7.2 * 3.14159265 = 22.6194671 with rounded values for pi and the resulting circumference.
That was William Jones, from England, in 1705
10log10 (p1 /p0 ) where the pi are power values.