已知函数f(x)=2cosxsin(x-π/3)+根号3 sin平方x+sinxcosx。

2个回答

  • (1) f(x)=2cosxsin(x-π/3)+√3 sin^2x+sinxcosx

    =2cosx[1/2sinx-√3/2cosx)+√3/2[1-cos2x]+1/2sin2x

    =1/2sin2x-√3cos^2x-√3/2cos2x+1/2sin2x+√3/2

    =sin2x-√3/2cos2x-√3/2cos2x+√3/2-√3/2

    =sin2x-√3cos2x

    =2sin(2x-π/3)

    函数y=f(x)图像的对称中心:(π/6,0)

    (2) 4sin(2x-π/3)-m+1 在【π/6,7π/12】有两个相异的实根

    当x=π/6时, 4sin(2x-π/3)-m+1=-m+1

    当x=7π/12时, 4sin(2x-π/3)-m+1=4sin(5π/6)-m+1=2-m+1=3-m

    (4sin(2x-π/3)-m+1)'=8cos(2x-π/3)=0 x=5π/12

    当x0; 当x>5π/12时,导数0 且 -m+1