We know that sin(2α)=2sin(α)cos(α) and cot(α)=sin(α)cos(α). Substituting these into the expression, we get:
sin(2α)⋅2cot(α)=2sin(α)cos(α)⋅2sin(α)cos(α) =2sin(α)cos(α)⋅2sin(α)cos(α) =2sin(α)2sin(α)cos2(α) Assuming sin(α)=0, we can cancel the 2sin(α) terms from the numerator and denominator. =cos2(α)