Question

Two vectors and their resultant all have the same magnitude. Find the angle between them.

Answer 1

$\overrightarrow{a},\overrightarrow{b}$ are two vectors has same magnitude $K$

$K=\sqrt{a^2+b^2+2ab\cos \theta }$

$\Rightarrow K=\sqrt{K^2+K^2+2K^2\cos \theta }$

$\cos \theta =-\frac{1}{2}$

$\Rightarrow \theta ={240}^o$