Question

已知向量|OA=|a|=3 |OB|=|b|=3,∠AOB=90°,则|a+b|=

Answer 1

|a+b|^2

=(a+b)^2

=a^2+b^2+2a*b

=|a|^2+|b|^2+2a*b

=9+9+2*3*3*cos90°

=18

|a+b|=3√2