Question

Find all solutions to cos(5x) = -1.

I know that the end answer should be somehow in the form of "x= ? +k(2π)" and I think that 3π/2 is what goes in place of the questionmark but I'm not sure how the problem is affected by it being 5xinstead of just x.

Please show and explain how you solve the problem so I canunderstand the correct methodology for it.

Thanks!