2sin^2-sinxcosx-cos^2=1
问题描述：
2sin^2-sinxcosx-cos^2=1
答
2sin^2x-sinxcosx-cos^2x=sin^2x+cos^2xsin^2x-sinxcosx-2cos^2x=0(sinx-2cosx)*(sinx+cosx)=0sinx-2cosx=0或sinx+cosx=0即有tanx=2,或tanx=-1即有x=Pai+arctan2或kPai-Pai/4