已知函数f(x)=cos2x/[sin(π/4-x)]

问题描述:

已知函数f(x)=cos2x/[sin(π/4-x)]

cos2x=sin(π/2-2x)=2sin(π/4-x)cos(π/4-x)
cos2x/[sin(π/4-x)]
=2sin(π/4-x)cos(π/4-x)/[sin(π/4-x)]
=2cos(π/4-x)/