Practicing Success
If $|\vec a-\vec b|=|\vec a|=|\vec b|=1$, then the angle between $\vec a$ and $\vec b$, is |
$\frac{π}{3}$ $\frac{3π}{4}$ $\frac{π}{2}$ 0 |
$\frac{π}{3}$ |
Let θ be the angle between $\vec a$ and $\vec b$. $|\vec a-\vec b|=1$ $⇒|\vec a-\vec b|^2=1$ $⇒|\vec a|^2-|\vec b|^2-2(\vec a.\vec b)=1$ $⇒|\vec a|^2-|\vec b|^2-2|\vec a||\vec b|\cos θ =1$ $⇒1+1-2\cos θ =1$ $⇒2\cos θ =1⇒\cos θ=\frac{1}{2}⇒θ=\frac{π}{3}$ |