已知tanα=-1/2,则（1+2sinαcosα）/(sin^2-cos^2)的值为_________.
问题描述：
已知tanα=-1/2,则（1+2sinαcosα）/(sin^2-cos^2)的值为_________.
答
（1+2sinαcosα）/(sin^2-cos^2)=(sin²a+cos²a+2sinacosa)/(sina-c0sa)(sina+cosa)=(sina+cosa)²/(sina-cosa)(sina+cosa)=(sina+cosa)/(sina-cosa)tana=-1/2分子分母同时除以cosa得=(tana+1)/(tana-...