Question

已知(sinα+3cosα)/(3cosα-sinα)=5 则sin^2α-sinαcosα的值是

Answer 1

已知条件上下同除以cosα 得到(tanα+3)/(3-tanα)=5 解得tanα=2 所求式子等于（sin^2α-sinαcosα）/1=(sin^2α-sinαcosα)/(sin^2α+cos^2α)=(tan^2α-tanα)/(tan^2α+1)=2/5 望采纳!