These all algorithms are interactive. Some of them can be modified and re-run again by clicking upper right part of the code part. Visit Convex Hull and Smallest Enclosing Circle first. They are well documented algorithms for modifying.
Convex Hull
Well know Convex Hull problem is coded here. It is very basic algorithm in Computational Geometry.
Smallest Enclosing Disk
Problem of finding smallest circle that contains all of a given set of points in the Euclidean plane.
L-monotone
Polygon P in the plane is called monotone with respect to a straight line L. What is this L?
Dual Line
This application shows dual of a 2D point as a line in xy-coordinate system.
Stabbery Checking
Checking line for stabbery? If intersection exists there must be a line intersects all line segments.