Q. The value of $\cos{15{^\circ}\cos{7\frac{1}{2}{^\circ}\sin{7\frac{1}{2}{^\circ}}}}$ is
A) $\frac{1}{2}$
B) $\frac{1}{8}$
C) $\frac{1}{4}$
D) $\frac{1}{16}$
Explanation
(b)
$\cos{15{^\circ}\cos 7}\frac{1}{2}{^\circ}\sin 7\frac{1}{2}{^\circ}$
$= \frac{1}{2}\cos{15{^\circ}\sin{15{^\circ} = \frac{1}{4}\sin{30{^\circ}}}}$
$= \frac{1}{4} \times \frac{1}{2} = \frac{1}{8}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.