If the magnitude of sum of two vectors is equal to the magnitude of difference of the two vectors, the angle between these vectors is
Let the two vectors be A→ and B→ .
Then, magnitude of sum of A→ and B→ ,
and magnitude of difference of A→ and B→ ,
or A2+B2+2ABcosθ=A2+B2-2ABcosθ⇒4ABcosθ=0∵4AB≠0, ∴cosθ=0 or θ=90°