|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