(1+tanθ+cotθ)(sinθ−cosθ)=(secθcosec2θ−cosecθsec2θ)
LHS=(1+tanθ+cotθ)(sinθ−cosθ)=(1+sinθcosθ+cosθsinθ)(sinθ−cosθ)=(1+sin2θ+cos2θsinθ cosθ)(sinθ−cosθ)=(1+1sinθ cosθ)(sinθ−cosθ)=(1+sinθ cosθ)(sinθ−cosθ)sinθ cosθRHS=(secθcosec2θ−cosecθsec2θ)=sin2θcosθ−cos2θsinθ=sin3θ−cos3θsinθ cosθ=(sinθ−cosθ)(sin2θ+cos2θ+sinθ cosθ)sinθ cosθ [∵a3−b3=(a−b)(a2+b+ab)]=(1+sinθ cosθ)(sinθ−cosθ)sinθ cosθLHS=RHS