Question

What is the angle between vector A and vector B for which |A+B|=|A-B|.
Plz give explanation it's too much important for me

Answer 1

A2 + B2 + 2ABcosθ = A2 + B2 - 2ABcosθ

2ABcosθ = -2ABcosθ

If A ≠ 0 and B ≠ 0, then

cosθ = -cosθ ⇒

cosθ = 0 ⇒ θ = 90°