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AP EAMCET · Maths · Trigonometric Ratios & Identities

\(\sin ^3 10^{\circ}+\sin ^3 50^{\circ}-\sin ^3 70^{\circ}=\)

  1. A \(\frac{-3}{8}\)
  2. B \(\frac{3}{4}\)
  3. C \(\frac{\sqrt{3}}{2}\)
  4. D \(\frac{-1}{3}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(\frac{-3}{8}\)

Step-by-step Solution

Detailed explanation

Apply the identity \(\sin^3 x + \sin^3(60^{\circ}-x) - \sin^3(60^{\circ}+x) = -\frac{3}{4}\sin 3x\). Substitute \(x=10^{\circ}\): \(\sin ^3 10^{\circ}+\sin ^3 (60^{\circ}-10^{\circ})-\sin ^3 (60^{\circ}+10^{\circ}) = -\frac{3}{4}\sin (3 \times 10^{\circ})\).…