Q. If $\cos^{2}{\theta = \cos{2\theta}}$, then the general value of $\theta$ is
A) $n\pi$
B) $2n\pi$
C) $\frac{n\pi}{3}$
D) $\frac{n\pi}{2}$
Explanation
(a)
We have, $\cos^{2}{\theta = \cos{2\theta}}$
$\Rightarrow \ \cos^{2}{\theta = {2\cos^{2}}{\theta - 1}}$
$\Rightarrow \ \cos^{2}\theta = 1\ \Rightarrow \ \theta = n\pi$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.