Question

Q.13 Determine the angle between two vectors A and B if |Ā + B 1 = |Ā-Bl​

Answer 1

squaring on both sides

|A+B|^2=|A-B|^2

|A|^2+|B|^2+cos(AB)=|A|^2+|B|^2-cos(AB)

2cos(AB)=0

cos(AB)=cos90°

AB=90°