Two forces are such that the sum of their magnitude is 18N and their resultant which has magnitude 12N, is perpendicular to the smaller force. Then the magnitudes of the forces are
13N, 5N
A+B=18 ------(1)
122=A2+B2+2AB cosθ
tanα=BsinθA+Bcosθ⇒A+Bcosθ=0
or cosθ=−A/B
144=A2+B2−2A2orB2−A2=144 --------(2)
Solving(1)&(2)B=13N; A=5N