ok so I have the problem ycos(x^2)dxdy with parameters dx=y^2 to 1 and dx=0 to 1 the first problem I have is integrating cos with respect to x^2. is it a double angle identity? the second is how do I go further if Y^2 gets added into the mix later? The attempts I have made have made me even more confused than before. I looked up how I could integrate cos x^2 and could not find a clear answer. Help is appreciated.