(sinθ+cosθ)/(sinθ-cosθ) >0即(sinθ+cosθ)(sinθ-cosθ) >0sin²θ-cos²θ>0sin²θ>cos²θ若cosθ=0则sinθ=±1,成立θ=kπ+π/2若cosθ≠0则两边除以cos²θ>0且sinθ/cosθ=tanθ所...