MCQ
$8 \sin \frac{x}{8} \cos \frac{x}{2} \cos \frac{x}{4} \cos \frac{x}{8}$ is equal to
  • A
    $8 sin x$
  • $sin x$
  • C
    $cos x$
  • D
    $8 cos x$

Answer

Correct option: B.
$sin x$
(B)
$8 \sin \frac{x}{8} \cos \frac{x}{2} \cos \frac{x}{4} \cos \frac{x}{8}$
$=4\left(2 \sin \frac{x}{8} \cos \frac{x}{8}\right) \cos \frac{x}{2} \cos \frac{x}{4}$
$=4\left(\sin \frac{x}{4} \cos \frac{x}{2} \cos \frac{x}{4}\right)$
$\ldots[\because 2 \sin A \cos A=\sin 2 A]$
$=2\left(2 \sin \frac{x}{4} \cos \frac{x}{4}\right) \cos \frac{x}{2}$
$=2 \sin \frac{x}{2} \cos \frac{x}{2}=\sin x$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free