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AP EAMCET · Maths · Trigonometric Ratios & Identities

If \(x+\frac{1}{x}=2 \sin \alpha\) and \(y+\frac{1}{y}=2 \cos \beta\), then \(x^3 y^3+\frac{1}{x^3 y^3}=\)

  1. A \(2 \cos 3(\beta-\alpha)\)
  2. B \(2 \cos 3(\beta+\alpha)\)
  3. C \(2 \sin 3(\beta-\alpha)\)
  4. D \(2 \sin 3(\beta+\alpha)\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(2 \sin 3(\beta-\alpha)\)

Step-by-step Solution

Detailed explanation

It is given that \(\begin{array}{l} x+\frac{1}{x}=2 \sin \alpha \Rightarrow x=\sin \alpha+i \cos \alpha=\cos \left(\frac{\pi}{2}-\alpha\right) +i \sin \left(\frac{\pi}{2}-\alpha\right) \\ \Rightarrow \quad x=e^{i\left(\frac{\pi}{2}-\alpha\right)} \end{array}\) and…