Q. What is the angle between ($\widehat{i} + 2\widehat{j} + 2\widehat{k}$) and $\widehat{i}$
A) $0{^\circ}$
B) $\pi/6$
C) $\pi/3$
D) None of these
Explanation
(d) cos$\theta = \frac{\left( \widehat{i} + 2\widehat{j} + 2\widehat{k} \right).\ \widehat{i}}{\left( 1^{2} + 2^{2} + 2^{2} \right)^{1/2}}$= $\frac{1}{\sqrt{3}} = \frac{1}{3}$
$= 0.4472 = \cos 63{^\circ}12'$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.