My attempt:
I used the distributive rule to expand it, and got:
I recognise that
So I get
=
=
I'm unsure if this is correct, since I don't have a solution. Any assistance would be greatly appreciated.
(notice the i's in the exponents). So either the problem should read , or the solution should have cosh instead of cos. If the problem should have had i's in the exponents then the solution is correct.