设函数f(X)=sin(πx/4-π/6)-2cos^2 π/8x+1

1个回答

  • f(x)=sin(πx/4-π/6)-2cos²(πx/8)+1

    =sin(π/4)xcos(π/6)-cos(π/4)xsin(π/6)-cos(π/4)x

    =√3/2sin(π/4)x-3/2cos(π/4)x

    =√3sin[(π/4)x-(π/3)]

    在g(x)的图像上任取一点(x,g(x) ),它关于x=1的对称点(2-x,g(x) )

    ∴点(2-x,g(x) )在y=f(x)的图像上

    从而g(x)=f(2-x)=√3sin[(π/4)(2-x)-(π/3)]=√3sin[(π/2)-(π/4)x-(π/3)]=√3cos[(π/4)x+(π/3)]

    当0≤x≤4/3时,π/3≤(π/4)x+(π/3)≤2π/3时

    ∴y=g(x)在区间[0,4/3]上的最大值是:gmax=√3cos(π/3)=√3/2