Question

If the magnitude of two vectors and their resultant are same. What is the angle between two vectors.

Answer 1

$R=A=B$ (given)

$R=\sqrt{A^2+B^2+2AB\cos \theta }$

$R^2=A^2+B^2+2AB\cos \theta$

$⟹A^2=A^2+A^2+2A^2\cos \theta$

$⟹\cos \theta =\frac{-1}{2}$

$⟹\theta ={120}^o$