F(X)=5根号3cos²X+根号3sin²X+4sinXcosX-3根号3 (1)求F(X)周期X

3个回答

  • f(x)=5√3*cos²x+√3*sin²x+4sinx*cosx-3√3

    =4√3*cos²x+4sinx*cosx-2√3

    =2√3*(2cos²x-1)+2*2sinx*cosx

    =2√3*cos2x+2*sin2x

    =4*(√3/2*cos2x+1/2*sin2x)

    =4(cos2x*sinπ/3+sin2x*sinπ/3)

    =4*sin(2x+π/3).(你化错了)

    最小正周期:T=2π/2=π,

    x∈[0,π]时,

    2x+π/3∈[π/3,7π/3],

    f(x)=4*sin(2x+π/3)∈[-4,4].

    f(x)最大值:4,此时x=π/12;

    最小值:-4,此时x=7π/12.

    因为y=sinx (x∈R),的单调递增区间为:[2kπ-π/2,2kπ+π/2],

    由2kπ-π/2