对的
f'(0)=lim(t->0) [f(0+t)-f(0)]/t
=lim(t->0) [f(-0-t)-f(0)]/t
=lim(t->0) [f(0-t)-f(0)]/t
=-lim(t->0) [f(0-t)-f(0)]/(-t)
=-f'(0)
f'(0)=0
对的
f'(0)=lim(t->0) [f(0+t)-f(0)]/t
=lim(t->0) [f(-0-t)-f(0)]/t
=lim(t->0) [f(0-t)-f(0)]/t
=-lim(t->0) [f(0-t)-f(0)]/(-t)
=-f'(0)
f'(0)=0