Integral Calculus Question 124

Question: $ \int_{{}}^{{}}{{{\sin }^{3}}x\ .\ \cos x\ dx=} $

[SCRA 1996]

Options:

A) $ \frac{{{\sin }^{4}}x{{\cos }^{2}}x}{8}+c $

B) $ \frac{{{\sin }^{4}}x}{4}+c $

C) $ \frac{{{\sin }^{2}}x}{2}+c $

D) $ 4{{\sin }^{4}}x+c $

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Answer:

Correct Answer: B

Solution:

$ \int_{{}}^{{}}{{{\sin }^{3}}x,.,\cos x,dx} $ . Put $ \sin x=t, $ then $ \cos x,dx=dt $ ; $ \int_{{}}^{{}}{t^{3}dt}=\frac{t^{4}}{4}=\frac{{{\sin }^{4}}x}{4}+c $ .