In this post I don't intend to share one more Euler's biography. You can always find that on the internet. My objective in this section is to give the reader my opinion on what I think was the life of these mathematicians.

I was thinking a while on which mathematician should I choose first. And I concluded that Euler was the man.

First of all I would like to say that he was the most prolific mathematician of all time. He wrote about 900 books! His theorems are to be found on almost all branches of math.

But let's talk about his life. Leonhard Euler was the father of 13 children. He had to live the very bad moment of burying one of them. So in the end he was the father of "only" 12.Try to imagine a house full of kids and a wife. Where do you get the time and strength to do more than 2000 theorems? Nevertheless he made it.

At around age 30 he started to lose the right eye's sight. And at 50 the left one's. So he had to live part of his life as a blind man. But this fact did not imply less mathematics. To the contrary very notable contributions were found after he lost his second eye.

Euler, who never worked as a professor, had his doctoral thesis revised and approved by Johann Bernoulli. We owe Leonhard the following contributions :

THE NUMBERS e AND i, THE CONNECTION BETWEEN THE TRIGONOMETRIC FUNCTIONS AND THE EXPONENTIAL, THE F + V - E = 2 FORMULA FOR PLANAR GRAPHS FROM WHICH TOPOLOGY WAS BORN, THE EULERIAN INTEGRALS AMONG THEM THE GAMMA FUNCTION, THE EULER PHI FUNCTION OF NUMBER THEORY, THE APPROXIMATE SOLUTIONS OF DIFFERENTIAL EQUATIONS OF FIRST ORDER, THE FUNDAMENTAL EQUATION OF THE CALCULUS OF VARIATIONS, THE EXPRESSION OF THE EXPONENTIAL FUNCTION AS A LIMIT OF THE POWER (1+X/n)^n, THE PATHS ON EULERIAN GRAPHS, THE EQUATIONS OF CAUCHY-RIEMANN WERE ALREADY WELL KNOWN TO HIM, THE SAME WITH GREEN'S THEOREM, ETC, ETC, ETC.

On September 18th 1783 his soul left our world.

On April 15th 2013 he was featured at Google's homepage.