you must use the two following identities.
Can you take it form here, if you need help proving those identities just ask.
Here is an interesting problem I'm having some difficulty with:
Find all the complexes z that satisfy the equation:
cos(z) = cosh(z).
The answer should be z=k(pi)(1+i) & z=k(pi)(1-i), but I don't know how to show this.
Any help, folks?