Int[(cos(3x))^2]

Can someone help me with this too? I'll return the thumbsup tomorrow. I'm really exhausted.

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- Nov 15th 2013, 07:24 AMDarrylcwcAnother integration
Int[(cos(3x))^2]

Can someone help me with this too? I'll return the thumbsup tomorrow. I'm really exhausted. - Nov 15th 2013, 08:11 AMSlipEternalRe: Another integration
By the double angle formula for cosine: . Add one to both sides, then divide both sides by two. So, . Plug in for . Now, you have:

Now, you can apply the power rule on the first integral and use the substitution for the second.