cos^2x是什么意思??cos(2x)还是cosx的平方??说清楚 f(x)=5√3cos^2x+√3sin^2x-4sinx cosx=4√3cos^2x-2sin2x+√3=2√3cos2x-2sin2x+3√3 =4cos(2x+π/3)+3√3x∈[π/4, 7π/24]则有2x+π/3∈[5π/6, 11π/12]最小值为f(7π/24)=4cos(11π/12)+3√3=-4cos(π/12)+3√3=3√3-√2-√6