Question

cos 3x + cos x/sin 3x + sin x = cot2x

Answer 1

hint :
cosA + cosB = 2cos[(A+B)/2]cos[(A-B)/2] and
sinA + sinB = 2sin[(A+B)/2]cos[(A-B)/2][(A-B)/2]

Answer 2

Need a better "hint" or an example or better yet show me how to "fish"