Question

已知向量a=6,向量b=8,向量a-向量b的绝对值=10,则向量a+向量b=

Answer 1

|a| =6,|b|=8 ,

|a-b| =10

|a-b|^2 = (a-b).(a-b) = 100

|a|^2+|b|^2 - 2a.b = 100

36 + 64 -2a.b =100

a.b = 0

|a+b|^2

= (a+b).(a+b)

=|a|^2+|b|^2+ 2a.b

= 100

|a+b| = 10