/// <summary>
/// Returns an array of two points, or null if tangent not possible.
/// Never returns a single point, even if booth points are equal.
/// </summary>
public static Point2d[] CirclePoint(Circle2d ci, Point2d pt)
{
Circle2d tc = Circle2d.From2Points(ci.Center, pt);
Point2d[] pts = Intersect2d.CircleCircle(tc, ci);
if (pts == null)
{
return(null);
}
if (pts.Length == 1)
{
Array.Resize(ref pts, 2); pts[1] = pts[0];
}
return(pts);
}
