Help with code

I have some code and I’m not sure how it works, would be great f someone could help with this bit of code:

_root.Bluespeed = .98;
x = Math.sin(_rotation
y = Math.cos(_rotation
//if you remove the below ! the car will not move. WHY?
if (!, _y+y, true)) {
_x += x;
_y += y;
} else {
_root.Bluespeed *= -.6;
it seems to me like all it should is rebound the car when the car hits, but if you take the code the car won’t move. really I just need help with Math part of it