第1个回答 2019-12-04
f(x)
=x^α.sin(1/x) ; x≠0
=0 ; x=0
(1)
lim(x->0) x^α.sin(1/x) =0
=>α>0
ie
α>0 , x=0, f(x) 连续
(2)
f'(0)
=lim(h->0) [h^α.sin(1/h) -f(0)]/h
=lim(h->0) h^(α-1).sin(1/h)
=0
=>α>1
ie
α>1 , x=0, f(x) 可导
(3)
x≠0
f(x)=x^α.sin(1/x)
f'(x)=αx^(α-1).sin(1/x) -x^(α-2).cos(1/x)
lim(x->0) f'(x) =0
=>α>2
α>2 , x=0, f(x) 的导数连续