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AP EAMCET · Maths · Indefinite Integration

\(\int \frac{d x}{4+5 \cos x}=\)

  1. A \(-\frac{1}{3} \log \left|\frac{3+\tan \frac{x}{2}}{3-\tan \frac{x}{2}}\right|+C\)
  2. B \(\frac{1}{3} \log \left|\frac{3+\tan \frac{x}{2}}{3-\tan \frac{x}{2}}\right|+C\)
  3. C \(-\frac{1}{9} \log \left|\frac{3-\tan \frac{x}{2}}{3+\tan \frac{x}{2}}\right|+C\)
  4. D \(\frac{1}{9} \log \left|\frac{3-\tan \frac{x}{2}}{3+\tan \frac{x}{2}}\right|+C\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{1}{3} \log \left|\frac{3+\tan \frac{x}{2}}{3-\tan \frac{x}{2}}\right|+C\)

Step-by-step Solution

Detailed explanation

\(\begin{aligned} & \text {Let } I=\int \frac{1}{4+5 \cos x} d x \\ & =\int \frac{1}{4+5\left(\frac{1-\tan ^2 x / 2}{1+\tan ^2 x / 2}\right)} d x \end{aligned}\) Let \(u=\tan \frac{x}{2} \Rightarrow \frac{d u}{d x}=\frac{\sec ^2 \frac{x}{2}}{2} d u\)…