rotate method
Create new CustomPoint whose x and y values are rotated by radians
in clockwise fashion
Implementation
CustomPoint<double> rotate(num radians) {
if (radians != 0.0) {
final cos = math.cos(radians);
final sin = math.sin(radians);
final nx = (cos * x) + (sin * y);
final ny = (cos * y) - (sin * x);
return CustomPoint<double>(nx, ny);
}
return CustomPoint(x.toDouble(), y.toDouble());
}