00:01
I think what makes this problem so difficult is cosine squared of x is in a lot of different trig identities.
00:07
I believe the one they want you to use, though, is that 2 cosine squared of x minus 1.
00:13
So look through it, a google internet search, that 2 cosine square of x minus 1 is equal to cosine of 2x.
00:23
And the reason why that should be your go -to is because you can solve for this and add one over and then divide everything by two.
00:33
So i'm going to write as one -half cosine of 2x plus 1 -half.
00:38
So if i go back to the original problem where they asked you to do the integral of cosine squared of x, well, i forgot to write dx.
00:47
That's going to equal the integral of 1 -half cosine of 2x plus 1 -half dx.
00:55
And now you can evaluate this integral...