做过的原题f(x)=3sin^2x+2√3sinxcosx+5cos^2x =sin^2 x+2√3sinxcosx+3cos^2 x+2(sin^2 x+cos^2 x) =sin^2 x+2√3sinxcosx+(√3)^2·cos^2 x+2 =(sinx+√3cosx)^2+2 =[√(1^2+(√3)^2)·sin(x+arctan(√3/1)]^2+2 =...