Why do we use pi?

Answer 1

The ancient civilisations, 4000 years ago, Sumerians, calculated 'pi' to be 3.141592.....

The story goes ; A donkey on a tether ( radius) was driven around in a circle (Circumference) to drive water up from a well.

They noticed that however, long the tether (radius) was , the correspodning circle(circumference) was always in the same ratio. ; pi = 3.141592.....

This can be mathematically expressed as

Circumference is directly proportional to the diameter.

or

'C' is directly proportional to 'd '

This can be equated with a constant

C = k d

Algebraically rearranged as

k = C/d

Whatever the dimensions of a given circle were/are 'k', the constant, was always found to be 3.141592....

Much later after the Sumerians, the Classical Greeks, gave the name 'pi' to this constant. 'pi' being the lower case classical Greek letter 'p' and refers to **P**roportion.

Hence 'pi' , today is used as this constant of proportion for circles.

'pi' is an irrational number, which means in casual terms, the decimal digits go to infinity and there is no regular order in the decimal digits.

On 'Supa-Dupa' computers' pi' has been calculated to some 50 billion places and still going.

NB Remember the circle equations.

C = pi d

C = 2 pi r ( d = 2r)

A(area) = pi r^(2)

When learning circle calculations you are probably given pi as 3.14, or .3.1416. or 22/7, but these are only approximate values, and NOT exact values.

Hope that helps!!!!!

Answer 2

We use it to calculate the circumference of a circle.