Question

# The resultant C of A and B is perpendicular to A also|a| |=| |c| the angle between A and B is

Solution

c=A+B

C.A=0

(A+B).A=0

A²+AB-cos(0)=0

(0 is L between A&B)

0=cos-1(-a/b)

[d²=|A|²+|b|²-2AB.cos0

|C|=|A| = 0= cos-1(b/2a)