He proved that pi is an irrational number.
the number is that you use for pi is 3.14 the number is that you use for pi is 3.14
pi is 3.14159
The first proof of the irrationality of Pi was done by J.H. Lambert in 1768
To find a number in Pi, see the link below
Pi is an irrational number; it can't be represented as a fraction of two integers. It has been proved that the majority of real numbers are irrational. The proof that pi is irrational was found in 1770; it's slightly too complicated to put in this answer, but if you search with google for pi irrational proof then you will find several different proofs.
No there is no exact proof because all we know is that the value of pi is a circle's circumference divided by its diameter which is an irrational number that has never been finally determined.The existence of pi needs no proof, it exists by definition and has a well defined known value by that definition. However as pi is an irrational number that value cannot be written completely in any standard number base system .
Ferdinand von Lindemann.