Desperate trig integration help needed! (1 Viewer)

[Molly07]

Ok, so this might be a bit last minute, seeing as my test is tomorrow, but can anyone tell me how to do the integral of cos^2(2x)?? i think it probably has something to do with the manipulation of that formula:
1/2x + 1/4sin2x + C
but i just can't get it out. Can anyone out there help?

 

[SoulSearcher]

You know that cos2@ = 2cos²@ - 1
Let @ = 2x, then
cos4x = 2cos²2x - 1
Therefore 1 + cos4x = 2cos²2x
cos²2x = (1+cos4x)/2

You can integrate that now.

 

[conman]

You have to remember any thing which includes a trig square have to be converted using double angle formula.