## Sunday, April 15, 2007

### Leonhard Euler

Leonhard Euler (pronounced Oiler) was born on April 15, 1707 and died on September 7, 1783. He was a Swiss mathematician who was tutored by Johann Bernoulli. He worked at the Petersburg Academy and Berlin Academy of Science. He had a phenomenal memory, and once did a calculation in his head to settle an argument between students whose computations differed in the fiftieth decimal place. Euler lost sight in his right eye in 1735, and in his left eye in 1766. Nevertheless, aided by his phenomenal memory (and having practiced writing on a large slate when his sight was failing him), he continued to publish his results by dictating them. Euler was the most prolific mathematical writer of all times finding time (even with his 13 children) to publish over 800 papers in his lifetime. He won the Paris Academy Prize 12 times. When asked for an explanation why his memoirs flowed so easily in such huge quantities, Euler is reported to have replied that his pencil seemed to surpass him in intelligence. François Arago said of him "He calculated just as men breathe, as eagles sustain themselves in the air" (Beckmann 1971, p. 143; Boyer 1968, p. 482).

One of the most famous and appealing equations, $e^{i\pi} + 1 = 0$ (where $e$ is Euler's number, the base of the natural logarithm, $i$ is the imaginary unit, one of the two complex numbers whose square is negative one (the other is $-i$), and $\pi$ is pi, the ratio of the circumference of a circle to its diameter) was derived by him.