Let \(\vec{a}\) and \(\vec{b}\) be two unit vectors and \(\theta\) is the angle between them. Then \(\vec{a}+\vec{b}\) is a unit vector of
Answer & explanation
Correct answer: option 4
\(\begin{aligned}|\vec{a}+\vec{b}|^{2}&=1\\ 1+1+2\cos \theta&=1\\ \cos \theta&=-1\\ \theta &=\frac{2\pi}{3}\end{aligned}\)