(*) cotθ−cscθ+1cotθ+cscθ−1 (we have taken (cotθ−cscθ+1) instead of (cotθ+cscθ+1) as denominator) =cotθ−cscθ+1cotθ+cscθ−(csc2θ−cot2θ)=cotθ−cscθ+1cotθ+cscθ−(cscθ+cotθ)(cscθ−cotθ)=cotθ−cscθ+1(cotθ+cscθ)−(1−cscθ+cotθ)=cotθ+cscθ=sinθcosθ+sinθ1=sinθcosθ+1