已知:tana-1/tana=-1,求1/[sina^2+2sina·cosa-(cos^2)·a]得值

问题描述:

已知:tana-1/tana=-1,求1/[sina^2+2sina·cosa-(cos^2)·a]得值

sina/cosa-cosa/sina=-1(sin^2a-cos^2a)/sinacosa=-1sin^2a-cos^2a=-sinacosa1/[sina^2+2sina·cosa-(cos^2)·a]=1/sinacosa=sin^2a+cos^2a/sinacosa=sina/cosa+cosa/sina=tana+1/tanatana-1/tana=-1tan^2a+1/tan^2a...