(sina+cosa)/(sina-cosa)=(sina/cosa+cosa/cosa)/(sina/cosa-cosa/cosa)=(sina/cosa+1)/(sina/cosa-1)=(tana+1)/(tana-1)=(3+1)/(3-1)=2tana=sina/cosa=3sina=3cosa（2）1/（sin²a-sinacosa-2cos²a）=1/（...