> While surfing the net I found a comment that got my attention. So let
> me ask you a question. Is it true that the beautiful formula
> exp(ix) = cos x + i sen x
> was known before Euler discovered it in 1742?
>
To my knowledge, the beautiful Euler's formula
e^(sqr(-1) x) = cos x + sqr(-1) sen x
was NOT known before Euler (but, yes, others might disagree, especially
if they read p. 28 of Roger Cotes's _Harmonia mensurarum_ with a Whiggish
magnifying glass!).
Julio Gonzalez Cabillon