已知(tana-1)/tana=-1 求1/sin^2a+2sinacosa-cos^2a

问题描述:

已知(tana-1)/tana=-1 求1/sin^2a+2sinacosa-cos^2a

解tana-1=-tana2tana=1tana=1/21/(sin²a+2sinacosa-cos²a)=(sin²a+cos²a)/(sin²a+2sinacosa-cos²a) 分子分母同除以cos²a=(tan²a+1)/(tan²a+2tanx-1)=(1/4+1)/(1...