As depicted in the two figures here, let us consider that F1 is the force applied to pull the body upwards: F1 = mg (sin θ + µ cos θ) and F2 is the force applied to keep the body in position): F2 : mg (sin θ - µ cos θ)
However, we have F1 = 3F2 mg (sin θ + µ cos θ) = 3mg (sin θ - µ cos θ) 4µ cos θ = 2 sin θ ⇒ µ =