1. The problem statement, all variables and given/known data Complex Analysis Problem: The euler Numbers E_n, n=0, 1, 2,..., are defined by 1/cosh(z) = the sum from n=0 to n=infinity of E_n/n! z^n (|z|<pi/2). show that E_n=0 for n odd. Calculus E_0, E_2, E_4, E_6 2. Relevant equations Not entirely sure what to put here for this one. 3. The attempt at a solution I've been stuck on this one for a little while now. I started out by just writing out the terms. E_0+E_1*z+E_2/2! z^2+.... I know that the coshz is an even function, I know the first x amount of terms of Euler's Numbers, but I'm struggling on how to 'prove' that Odd Euler Numbers are = 0. Any guidance on getting me going here? Thank you kindly.