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TS EAMCET · Maths · Trigonometric Ratios & Identities

For some \(a, b, c \in \mathbf{R}\), if \(\sin 5 \theta=a \cos ^4 \theta \sin \theta+b \cos ^2 \theta \sin ^3 \theta+c \sin ^5 \theta\), then \(a b c=\)

  1. A -10
  2. B 10
  3. C 0
  4. D -50
Verified Solution

Answer & Solution

Correct Answer

(D) -50

Step-by-step Solution

Detailed explanation

Given, \(\sin 5 \theta=a \cos ^4 \theta \sin \theta+b \cos ^2 \theta \sin ^3 \theta+c \sin ^5 \theta\) at \(\theta=\frac{\pi}{2}\), we get \(1=0+0+c \Rightarrow c=1\) \(\ldots(\mathrm{i})\) at \(\quad \theta=\frac{\pi}{4}\), we get…