Practicing Success
Angle between vectors $\vec a$ and $\vec b$, where $\vec a, \vec b$ and $\vec c$ are unit vectors satisfying $\vec a+ \vec b + \sqrt{3}\vec c =\vec 0$, is |
$\frac{π}{6}$ $\frac{π}{4}$ $\frac{π}{3}$ $\frac{π}{2}$ |
$\frac{π}{3}$ |
We have, $\vec a+ \vec b + \sqrt{3}\vec c =\vec 0$ $⇒\vec a+ \vec b=-\sqrt{3}\vec c$ $⇒|\vec a+ \vec b|=\sqrt{3}|\vec c|$ $⇒|\vec a+ \vec b|^2=3|\vec c|^2$ $⇒|\vec a|^2+|\vec b|^2+2|\vec a||\vec b|\cos θ=3|\vec c|^2$, where θ is the angle between $\vec a$ and $\vec b$ $⇒1+1+2\cos θ=3⇒\cos θ=\frac{1}{2}⇒θ=\frac{π}{3}$ |