f﹙x,y﹚＝┏xsin﹙1/y﹚ y≠0┗0y＝0在﹙x,y﹚,当y≠0时,是初等函数,当然连续.在﹙0,0﹚,对ε＞0取δ＝ε＞0当√﹙x²+y²﹚＜δ时 |f﹙x,y﹚-f﹙0,0﹚|≤|x|≤√﹙x²+y
...