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TS EAMCET · Maths · Trigonometric Ratios & Identities

The period of \(\frac{\sin x}{\cos 3 x}+\frac{\sin 3 x}{\cos 9 x}+\frac{\sin 9 x}{\cos 27 x}+\frac{\sin 27 x}{\cos 81 x}\) is

  1. A \(\frac{2 \pi}{3}\)
  2. B \(\frac{\pi}{81}\)
  3. C \(2 \pi\)
  4. D \(\pi\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(\pi\)

Step-by-step Solution

Detailed explanation

Given, \(\frac{\sin x}{\cos 3 x}+\frac{\sin 3 x}{\cos 9 x}+\frac{\sin 9 x}{\cos 27 x}+\frac{\sin 27 x}{\cos 81 x}\) \(=\frac{1}{2}\left[\frac{2 \sin x \cos x}{\cos 3 x \cos x}+\frac{2 \sin 3 x \cos 3 x}{\cos 9 x \cos 3 x}+\frac{2 \sin 9 x \cos 9 x}{\cos 27 x \cos 9 x}\right.\)…