(1)(cosθ+sinθ)/(cosθ-sinθ)；
=(1+tanθ)/(1-tanθ)
=(1+√2)/(1-√2)
=-(1+√2)²
=-3-2√2


（2）sin²θ-sinθcosθ+2cos²θ
=(sin²θ-sinθcosθ+2cos²θ)/(sin²θ+cos²θ)
=(tan²θ-tanθ+2)/(tan²θ+1)
=(2-√2+2)/(2+1)
=(4-√2)/3