证明恒等式tan a*sin a/tan a-sin a=1+cos a/sin a

(tanα∙sinα)/(tanα-sinα)=(tanα∙sinα)/[sinα(1/cosα-1)] =tanα/[(1/cosα)-1)]=(tanα∙cosα)/(1-cosα)=sinα/(1-cosα)=[sinα∙(1+cosα)]/[(1-cosα)(1+cosα)] =[sina∙(...