The angle between 2 vectors $\vec{a}$ and $\vec{b}$ with magnitude 1 and 2 respectively when $\vec{a} . \vec{b}=1$ is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → $\frac{\pi}{3}$
$|\vec{a}|=1$, $|\vec{b}|=2$
so $\vec a.\vec b=|\vec{a}||\vec{b}|\cos θ$
$⇒1=1×2\cos θ⇒\cos θ=\frac{1}{2}$
$θ=\frac{\pi}{3}$