Calculus integration problem: $\int \sin^5 (x) \cos^2 (x)\,dx$

What's the integration of $$\int \sin^5 (x) \cos^2 (x)\,dx?$$

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Share with us what you've tried so we can help you along. –  JohnD Feb 3 at 19:53

Hint: Write $$\sin^5(x)\cos^2(x)=(\sin^2(x))^2\cos^2(x)\sin(x).$$

Now use $\cos^2(x)+\sin^2(x)=1$ and do the appropriate change of variable.

This is the general method to integrate functions of the type $$\cos^n(x)\sin^m(x)$$ when one of the integers $n,m$ is odd.

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Using trig identities, you can show that: $$\sin ^5(x) \cos ^2(x)=\frac{5 \sin (x)}{64}+\frac{1}{64} \sin (3 x)-\frac{3}{64} \sin (5 x)+\frac{1}{64} \sin (7 x)$$
To do this, first use the "Power-reduction formulas" to reduce to get: $$\sin^5(x)=\frac{10 \sin x - 5 \sin 3 x+ \sin 5 x}{16}$$ $$\cos^2(x)=\frac{1 + \cos (2 x)}{2}$$ And then use: $$\cos (2 x) \sin (nx) = {{\sin((n+2)x) - \sin((n-2)x)} \over 2}$$