sinx * cosx / [(sinx)^2 + (cosx)^2] = -11 / (tanx + 1/tanx) = -1 (左边式子上下同除于sinx * cosx)tanx + 1/tanx = -1(tanx)^2 + 1 = -tanx(tanx)^2 + tanx + 1 =0(tanx + 1/2)^2 + 3/4 =0tanx 无解.题目错了吧....