已知函数f(x)=2sin(π/4+x)sin(π/4-x),则f(π/3)的值等于

问题描述:

已知函数f(x)=2sin(π/4+x)sin(π/4-x),则f(π/3)的值等于

已知函数f(x)=2sin(π/4+x)sin(π/4-x),
=2sin(π/4+x)cos(π/4+x),
=sin(π/2+2x)
=cos2x
f(π/3)=cos2π/3=-1/2