The square of the resultant of two forces 4 N and 3 N exceeds the square of the resultant of the two forces by 12, when they are mutually perpendicular. The angle between the vectors is
θ1 = 900, resultant is R1
θ2 = θ, resultant is R2 and R22 = R12 +12
P2+Q2 +2PQcosθ = P2 +Q2+12
2PQcosθ = 12 ⇒ 2(4)(3)cosθ=12
cosθ=1/2 ⇒θ=600