Moving Array Objects in a Ellipse (javascript)

I am making a race track in html and it is in the shape of an oval. If I have multiple cars (they're just images) moving at the same time on the same array, how would I be able to make them change direction when they approach the corner. I've seen a lot of examples but am still confused on how to use the sin and cos functions.

This may not be the best way, but an easy trick I found was to have some invisible object follow the path, then have your cars follow that invisible object, and use LookAt to orient it.