Use the binomial expansion (ie with coefficients from Pascal's triangle). Every second term will be an even power of i and hence real.
The question
Evaluate
I'm not sure what the weird R symbol means. I assume it wants me to find the real part of the solution?
Anyway, how do I find the solution to this power? I could split it into two perfect squares, but I'm sure there's a better way.
Any assistance would be great!