A helpful scientific calculator that runs in your web browser window.
Holt Online Learning

This website helps to find the measure of the fourth angle of a quadrilateral given the three other angle measures.
AAA Math

This site outlines the theorems about parallelograms with proofs to these theorems.
Steve Wilson of Sonoma State University

A page with links for properties of circles and different types of polygons. Each link has great visuals with clear markings, definitions, and formulas.
Cool Math

Describes the special relationships of the sides, angles, and diagonals of a rhombus.
Zona Land

Website gives a general overview of different types of quadrilaterals and how to identify them. Explains the properties of different quadrilaterals.
Math.com

Formula and description of the perimeter of a square.
Math Open Reference

Definiton and properties of the diagonals of a square
Math Open Reference

Area of a square. Definition and formula
Math Open Reference

Definition and properties of a square. Describes how it can be considered a special case of other types of quadrilateral. Links to other related topics, including the area of a square.
Math Open Reference
