当x∈(π/2,π)时,y=x/2∈(π/4,π/2)此时siny>cosy>0,则1+sinx=(sin(x/2)+cos(x/2))²1-sinx=(sin(x/2)-cos(x/2))²1+cosx=2cos²(x/2)1-cosx=2sin²(x/2)所以原式=2tanysiny,y=x/2∈(π/4,π/2)f(...