Archimedes' constant

The number pi has the value π = 3,1415…

Explanation

It is an irrational number, so you cannot write it as a quotient of two integers. For simple use you can of course take an approximation with the fraction

but nowadays, everyone has a calculator, which is just as easy.

History

The Swiss mathematician Leonhard Euler (1707 - 1783) used the Greek letter π as a symbol in his documents.