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Thread: trig integral

  1. #1
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    trig integral

    $\displaystyle \int\ cos^3xsin2x$

    i first split up $\displaystyle cos^3x$ into $\displaystyle cosx(1-sin^2(x))$ and i said $\displaystyle sin2x= 2sinxcosx$. this is apparently the correct approach, but when i did it on my quiz today, i ended up getting $\displaystyle -1/10 cos^5x +c $instead of $\displaystyle -2/5 cos^5x +c $. the latter is the correct answer.. can someone help me find my mistake?
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  2. #2
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    convert sin(2x) into 2sin(x)cos(x) and then you should be ready to integrate using the power rule with u substitution where u = cos(x)
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