3sin^2α-sinαcosα=(3sin^2α-sinαcosα)/1=(3sin^2α-sinαcosα)/(sin^2α+cos^2α)=(3tan^2α-tanα)/(tan^2α+1).分子分母同除cos^2α=(3*4-2)/(4+1)=10/5=2如果您认可我的回答,请点击“采纳为满意答案”,祝...