Q. $\frac{\left( \cos{\theta + i\sin\theta} \right)^{4}}{\left( \sin{\theta + i\cos\theta} \right)^{5}}$ is equal to

A) $\cos{\theta - i\sin\theta}$
B) $\sin{\theta - i\cos\theta}$
C) $\cos{9\theta - i\sin{9\theta}}$
D) $\sin{9\theta - i\cos{9\theta}}$
Explanation

(d)
$\frac{\left( \cos{\theta + i\sin\theta} \right)^{4}}{\left( \sin{\theta + i\cos\theta} \right)^{5}} = \frac{\left( \cos{\theta + i\sin\theta} \right)^{4}}{i^{5}\left( {\cos\theta}{- i\sin\theta} \right)^{5}}$
$= - i\ \left( \cos\theta + i\ \sin\theta \right)^{9}$
$= \sin{9\theta - i\cos{9\theta}}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.