Two vectors A and B have equal magnitudes. If magnitude of A + B is equal to n times the magnitude of A - B, then the angle between A and B is

Let θ be the angle between A and B,|A+B|=n| A-B| ⇒A2+B2+2ABcosθ=nA2+B2+2ABcos180°-θ 2x2(1+cosθ)=n2·2x2(1-cosθ)1+cosθ=n2-n2cosθ1+n2cosθ=n2-1 cosθ=n2-1n2+1θ=cos-1n2-1n2+1