Differential (and difference) Galois theorist, algorithmic analyst, and computer algebraist, and professor at North Carolina State University. Available here: books and papers, some in PDF, PostScript, or .dvi versions;...

This lesson from Illuminations asks students to measure the diameter and circumference of various circular objects, plot the measurements on a graph, and relate the slope of the line to π, the ratio of circumference to...

This site departs from the common themes taught in general geometry classes and introduces projective geometry, which has to do with special properties resulting from the intersection of lines, planes, and points. The...