(1)
f(x)=xsin(1/x),当x不等于0
lim(x->0)f(x)=lim(x->0)(xsin(1/x))=0=f(0),连续
f'(0)=lim(x->0)[f(x)-f(0)]/x=lim(x->0)sin(1/x),不存在,不可导
(2)
g(x)=x^2*sin(1/x^2),当x不等于0
lim(x->0)g(x)=lim(x->0)(x^2*sin(1/x^2))=0=g(0),连续
f'(0)=lim(x->0)[g(x)-g(0)]/x=lim(x->0)(xsin(1/x^2)=0,可导