Integral Calculus Question 379

Question: The value of $ \int_{{}}^{{}}{\frac{\sin x}{{{\cos }^{2}}x}\ dx} $ is

Options:

A) $ \sin x+k $

B) $ \tan x+k $

C) $ \sec x+k $

D) $ \tan x+\sec x+k $

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Answer:

Correct Answer: C

Solution:

Given $ I=\int_{{}}^{{}}{\frac{\sin x}{{{\cos }^{2}}x}},dx $ . Put $ \cos x=t\Rightarrow \sin x,dx=-dt $
$ \therefore ,I=\int_{{}}^{{}}{\frac{-dt}{t^{2}}}=\frac{1}{t}+k=\sec x+k $ .