Roman C. answered 11/13/15
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Masters of Education Graduate with Mathematics Expertise
U-Substitution: u = sin x, du = cos x dx
∫ cos3 x sin6 x dx
= ∫ (1 - sin2 x) cos x sin6 x dx
= ∫ (1 - u2)u6 du
= ∫ (u6 - u8) du
= u7/7 - u9/9 + C
= (sin7 x)/7 - (sin9 x)/9 + C