Q214 / 270 · NDA 2014 (Phase 2) · Mathematics

What is $\sin ^2 66 \frac{1}{2}^{\circ}-\sin ^2 23 \frac{1}{2}^{\circ}$ equal to?

  • A
    $\sin 47^{\circ}$
  • Correct answer
    B
    $\cos 47^{\circ}$
  • C
    $2 \sin 47^{\circ}$
  • D
    $2 \cos 47^{\circ}$

Solution

$\sin 90^{\circ} \cdot \sin \left(43^{\circ}\right)=\sin \left(90^{\circ}-47^{\circ}\right)=\cos 47^{\circ}$

Hence, the correct answer is option: 'B'.

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