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:
1800
00
900
450
|A→ +B→| = |A→ −B→| = θ = 900
(A)2+(B)2+2(A)(B)cosθ = (A)2+(B)2-2(A)(B) cosθ
2cosθ = 0 ⇒θ = 900