I was trying to prove that, given a set of points in 2d, the farthest distance must lie on the convex hull of this set of points. Any help would be apreaciated. thanks

Farthest distance of what? Farthest distance between 2 points? Must lie on the convex hull? As in, a line segment of the convex hull is the farthest distance? Or the endpoints lie on the convex hull?