#LHS=(sinθ-cosθ+1)/(sinθ+cosθ-1)#
#=(costheta(sinθ-cosθ+1))/(costheta(sinθ+cosθ-1))#
#=(costhetasinθ-cos^2θ+costheta)/(costheta(sinθ+cosθ-1))#
#=(costhetasinθ+costheta-(1-sin^2θ))/(costheta(sinθ+cosθ-1))#
#=(costheta(sinθ+1)-(1-sinθ)(1+sintheta))/(costheta(sinθ+cosθ-1))#
#=((sinθ+1)(costheta-1+sinθ))/(costheta(sinθ+cosθ-1))#
# =(sinθ+1)/(cosθ)=RHS#
Proved