f(x)=2cosxsin(x+π/3)-√3sin^2x+sinxcosx
=cosx(sinx+√3cosx)-√3(sinx)^2+sinxcosx
=2sinxcosx+√3[(cosx)^2-(sinx)^2]
=sin2x+√3cos2x
=2sin(2x+π/3)=x/50π,
<==>sin(2x+π/3)=x/100π,
由于|sin(2x+π/3)|<=1,所以只需考虑|x|<=100π,即-100π<=x<=100π.
200π是sin(2x+π/3)的200个周期,
画示意图知,y=sin(2x+π/3)最右边的一个周期的图像与直线y=x/100π只有1个交点,其他199个周期的图像与直线y=x/100π各有两个交点,所以共有399个交点,即所求方程有399个根.
f(x)=2cosxsin(x+π/3)-√3sin^2x+sinxcosx
=2cosx(1/2*sinx+√3/2*cosx) -√3sin^2x+sinxcosx
= sinxcosx+√3cos^2x-√3sin^2x+sinxcosx
=2 sinxcosx+√3(cos^2x-sin^2x)
=sin2x+√3 cos2x
=2 sin(2x+π/3)
令2x+π/3=kπ+π/2, k∈Z.
得:x=kπ/2+π/12, k∈Z.这就是对称轴方程。
令2x+π/3=kπ, k∈Z.
得:x=kπ/2-π/6, k∈Z.
对称中心为(kπ/2-π/6,0), k∈Z.