At what angle the vector (vec(A)+vec(B)) and (vec(A)-vec(B)) must act, so that the resultant is sqrt(A^(2)_B^(2))

At what angle the vector (vec(A)+vec(B)) and (vec(A)-vec(B)) must act,

1.	At what angle the vector (vec(A)+vec(B)) and (vec(A)-vec(B)) must act, so that the resultant is sqrt(A^(2)_B^(2))
Answer» `COS^(-1)((A^(2)-B^(2))/(A^(2)+B^(2)))` `cos^(-1)((A^(2)+B^(2))/(A^(2)-B^(2)))` `cos^(-1)((A^(2)-B^(2))/(2(A^(2)+B^(2))))` `cos^(-1)((A^(2)+B^(2))/(2(B^(2)-A^(2))))` ANSWER :D