∴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.