(sinθ+2cosθ)/(sinθ-cosθ) (上下同除以cosθ)
=(tanθ+2)/(tanθ-1)
=4那(sin^2θ+2cosθsinθ+1)=？(sin^2θ+2cosθsinθ+1)=(sin^2θ+2cosθsinθ)/1+1=(sin^2θ+2cosθsinθ)/(sin^2θ+cos^2θ) +1(上下同除以cos^2θ)=(tan^2θ+2tanθ)/(tan^2θ+1) +1=8/5+1=13/5