Euler is one of the greatest and most prolific mathematicians of all time. He wrote the first accessible books on calculus, created the theory of circular funct... » 

Euler is one of the greatest and most prolific mathematicians of all time. He wrote the first accessible books on calculus, created the theory of circular functions, and discovered new areas of research such as elliptic integrals, the calculus of variations, graph theory, and so on. It took hundreds of yearsfor his successors to develop in full the theories he began, and some of his themes are still at the center of today's mathematics. «