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TS EAMCET · Maths · Indefinite Integration

\(\int \frac{d x}{7+5 \cos x}\) is equal to

  1. A \(\frac{1}{\sqrt{3}} \tan ^{-1}\left(\frac{1}{\sqrt{3}} \tan \frac{x}{2}\right)+c\)
  2. B \(\frac{1}{\sqrt{6}} \tan ^{-1}\left(\frac{1}{\sqrt{6}} \tan \frac{x}{2}\right)+c\)
  3. C \(\frac{1}{7} \tan ^{-1}\left(\tan \frac{x}{2}\right)+c\)
  4. D \(\frac{1}{4} \tan ^{-1}\left(\tan \frac{x}{2}\right)+c\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{1}{\sqrt{6}} \tan ^{-1}\left(\frac{1}{\sqrt{6}} \tan \frac{x}{2}\right)+c\)

Step-by-step Solution

Detailed explanation

\text { Let } \begin{aligned} I & =\int \frac{d x}{7+5 \cos x} \\ & =\int \frac{d x}{7\left(\cos ^2 \frac{x}{2}+\sin ^2 \frac{x}{2}\right)+5\left(\cos ^2 \frac{x}{2}-\sin ^2 \frac{x}{2}\right)} \\ & =\int \frac{d x}{12 \cos ^2 \frac{x}{2}+2 \sin ^2 \frac{x}{2}} \\ & =\frac{1}{2}…