This problem coincides with my Calculus II course chapter on trigonometric integrals. I am unsure if I should be using the reduction formula for cosine or perhaps rewriting cosine as an even power and using the identity and then u substitution.

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- February 14th 2013, 04:37 PMjamesrbNeed help evaluating this integral.

This problem coincides with my Calculus II course chapter on trigonometric integrals. I am unsure if I should be using the reduction formula for cosine or perhaps rewriting cosine as an even power and using the identity and then u substitution. - February 14th 2013, 05:40 PMchiroRe: Need help evaluating this integral.
Hey jamesrb.

You may want to look at a reduction formula. You could expand everything out to get things in terms of sines and cosines (even squared ones) but there is a relationship for integrating powers of trig functions. - February 14th 2013, 06:01 PMProve ItRe: Need help evaluating this integral.
- February 15th 2013, 08:52 AMHallsofIvyRe: Need help evaluating this integral.
Generally speaking, any time you have an

**odd**power of cos(x) or sin(x), you can factor out one, leaving an even power. Then use " " or " to change to the "other" function, keeping that first term you factored out for the derivative:

Now, let u= sin(x) so that du= cos(x)dx and the integral becomes .

If you have only even powers of sine and/or cosine, then you will need and .