A searchable catalogue of hundreds of special triangle points (centroid, incenter, Hofstadter points, Yff centers, Apollonius point, etc.), with a glossary, collinearities, graphics, and links to biographical sketches of...

This geometry lesson from Illuminations presents a real-world problem for students to solve with mathematical functions. The material involves constructing the circumcenter and incenter of a triangle. Learners will gain...

Simple constructions; constructing regular polyhedra; symmetry; and some group theory.

In the introduction to this site we learn that, "A fundamental result of geometry, used often in secondary and collegiate mathematics, is the equality of ratios of corresponding sides in similar triangles." Accordingly,...

In general, a triangle is defined by its three elements. SAS, ASA, and SSS provide three well-known examples but there are many more. Bogomolny provides a table of constructions (linked to constructions) and invites...