translate method
Translates this coordinate by the given offsets. If a {@code goog.math.Coordinate} is given, then the x and y values are translated by the coordinate's x and y. Otherwise, x and y are translated by {@code tx} and {@code opt_ty} respectively. @return {!goog.math.Coordinate} This coordinate after translating.
Implementation
Coordinate translate(Coordinate tc)
{
this.x += tc.x;
this.y += tc.y;
return this;
}