∴Lim(x→0)y=2 exists,
The supplementary definition y( 1)=2 is continuous.
(3) Remove the absolute number, and the function is the following piecewise function:
When x>0, y = sinx/x; When x
Therefore, when x→0+, y→1; When x→0-, y→- 1.
Left and right limits exist but are not equal,
So x=0 is the first jump discontinuity.