f(x)=2cos²(x+π/12)+2sinxcosx-3 两倍角公式 2cos²(x+π/12)=1+cos2(x+π/12)=1+cos(2x+π/6)+sin2x-3=cos2x*cosπ/6-sin2x*sinπ/6+sin2x-2=cos2x*√3/2-sin2x*1/2+sin2x-2=√3/2cos2x+1/2sin2x-2=sin(2...