Why doesn't point's coordinate change even after modifiying object using controls? why the points remain same?

1. Drawn a polygon with three points :[{"x":60,"y":30},{"x":15.000000000000007,"y":55.98076211353316},{"x":14.999999999999986,"y":4.019237886466847}]
2. drag one point of triangle using control corner.
3. check for the object points
4. They remain same as that of those points with which I have drawn polygon