From GeoGebra Manual
- ClosestPoint[ <Path>, <Point> ]
- Returns a new point on a path which is the closest to a selected point.
- Note: For Functions, this command now uses closest point (rather than vertical point). This works best for polynomials; for other functions the numerical algorithm is less stable.
- ClosestPoint[ <Line>, <Line> ]
- Returns a new point on the first line which is the closest to the second line.