## cos^2(x) Integral..

1. The problem statement, all variables and given/known data
$\int cos^{2}x dx$

I know that

$cos^{2}x = \frac{1+cos2x}{2}$

but I don't see how that helps me.
Can someone help walk me through it..

2. Relevant equations

3. The attempt at a solution
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 Well, that leaves you with: $$\int \frac{1}{2}+\frac{1}{2}cos(2x)dx$$ Which you can break up into two integrals: $$\int \frac{1}{2}dx + \int \frac{1}{2}cos(2x)dx$$ The first one should be no problem. Isn't there some sort of substitution you can make for the second one?
 Recognitions: Homework Help Science Advisor Can you integrate cos(2x)? Use a u substitution.

## cos^2(x) Integral..

u=2x du=(1/2)dx
(1/2)∫cosudu
=(1/4)sin2x

So then..
x/2 + (1/4)sin2x
but thats not the answer..

Recognitions:
Homework Help
Science Advisor
 Quote by iRaid u=2x du=(1/2)dx (1/2)∫cosudu =(1/4)sin2x So then.. x/2 + (1/4)sin2x but thats not the answer..
I think it is the correct answer. You should probably put a +C on it. Is that the problem?

 Quote by Dick I think it is the correct answer. You should probably put a +C on it. Is that the problem?
Oh nevermind was looking at the wrong answer. Thanks for the help.
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