6
$\begingroup$

I'm struggling to integrate $\int \cos(2x)\cos(nx)\,\mathrm{ d}x$

I seem to be going round in circles and would be grateful if someone could help? I think I need to use a trig expansion or identity but I'm not sure which one?

Thanks =)

  • 2
    Are you familiar with the product-to-sum formulas?2011-05-04
  • 0
    It would be nice if you accept an answer, so that this question is not in the unanswered list.2011-05-06

2 Answers 2