Question

if moduls of vector A+B=mod of vectorA=mod of vector B then angle between vector A and B is

Answer 1

A^2+B^2+2ABcosn=A^2
B^2+2ABcosn=0
B+2Acosn=0------(1)
similarly
A^2+B^2+2ABcosn=B^2
A^2+2ABcosn=0
A+2Bcosn=0-------(2)
add 1 and 2
A+B+(A+B)2cosn=0
(A+B).2cosn= -(A+B)
cosn=-1/2
n=120 or n=240