Integral Calculus Question 293

Question: $ \int_{{}}^{{}}{\frac{dx}{\sin x+\sqrt{3}\cos x}}= $

Options:

A) $ \log \tan ( \frac{x}{2}+\frac{\pi }{2} )+c $

B) $ \frac{1}{2}\log \tan ( \frac{x}{2}+\frac{\pi }{6} )+c $

C) $ \log \cot ( \frac{x}{2}+\frac{\pi }{6} )+c $

D) $ \frac{1}{2}\log \cot ( \frac{x}{2}+\frac{\pi }{6} )+c $

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Answer:

Correct Answer: B

Solution:

$ \int_{{}}^{{}}{\frac{dx}{\sin x+\sqrt{3}\cos x}}=\frac{1}{2}\int_{{}}^{{}}{\frac{dx}{\frac{\sin x}{2}+\frac{\sqrt{3}}{2}\cos x}} $ $ =\frac{1}{2}\int_{{}}^{{}}{\frac{dx}{\sin ( x+\frac{\pi }{3} )}}=\frac{1}{2}\int_{{}}^{{}}{cosec( x+\frac{\pi }{3} )} $ $ =\frac{1}{2}\log \tan ( \frac{x}{2}+\frac{\pi }{6} )+c. $