Everything you wanted to know about prisms: what are lateral faces and edges; the difference between right and oblique prisms; how to calculate lateral area, total area and volume.

Using locus and Geometer's Sketchpad, this video demonstrates how ellipses and hyperbolas are related. Music is by Jan Hammer, from the Miami Vice soundtrack.

How to use more than one pair of congruent triangles to complete a proof.

How to classify triangles, and some important theorems involving the angles of triangles.

In this screencast, we define terms that are related to circles: center, radius, chord, diameter, tangent, concentric, inscribed, and circumscribed.

How to calculate the area of a regular polygon, using its apothem and perimeter.

An explanation of how to calculate the areas of trapezoids, with a few examples worked out.

This video explains how to create a kaleidoscope using Geometer's Sketchpad. I use this activity to teach reflections and dilations of objects.

An explanation of the tangent ratio for right triangles, and how it can be used to solve for sides and angles of right triangles.

An introduction to the exciting world of trapezoids.