Demonstrates how to calculate the area of two-dimensional shapes using formulas. Covers parallelogram, triangle, trapezoid, and circle. Includes a video modeling how to find the area of a circle and a triangle. [0:59]

A complete reference guide to diameters. It provides definitions, examples, and interactive activities that enhance further explanation. Includes links to related topics.

This site from the Rice University includes a fill-in-the-blank lesson on the definition of circles, as Pythagoras described.

This exhibit is designed to show students that geometry really does apply to the real world. By taking viewers through a home decoration project, students learn how to calculate area of a rectangle and circle.

This site from the Math Forum defines both a circular cylinder and a right circular cylinder. Pictures of each are provided. Formulas are provided.

This CoolMath resource provides an introduction to some Precalculus formulas.