A magnetic needle lying parallel to a magnetic field requires W units of work to turn it through 600 .What is the torque needed to maintain the needle in that position?

In the case of a dipole in a magnetic field. W=MBcosθ1-cosθ2and  Γ=MBsinθhere    θ1=00  θ2=60°    W=MB(1-cosθ)⇒W=MB2sin2θ/2             ∵(1-cosθ)=2sin2θ/2Dividing , ΓW=MBsinθMB2sin2θ/2=2sinθ2cosθ22sin2θ/2 ⇒ΓW=cotθ2⇒Γ=Wcot30°⇒Γ=3W