f(x)=cos(1/x),求f'(2/TT)
问题描述:
f(x)=cos(1/x),求f'(2/TT)
答
f(x)=cos(1/x)
f'(x)=-sin(1/x)*(1/x)'
=sin(1/x)*1/x^2
=π^2/4