tanθ=(sina-cosa)/(sina+cosa) =(tana-1)/(tana+1)=tan（a-45°）θ=α-45°或者θ=180°+α-45°=α+135°当θ=α-45°,sina-cosa/sinθ=sina-cosa/1/根号2（sinα-cosα）=根号2当θ=α+135°,sina-cosa/sinθ=si...