National Council of Teachers of Mathematics
The Math Forum: Problems Library Geometry Triangles
This site contains a wealth of problems that deal with the basic definitions of medians, altitudes, angle bisectors, and perpendicular bisectors or the defining characteristics of the different types of triangles. There are also...
Sophia Learning
Sophia: Using Triangles to Examine Quadrilaterals: Lesson 5
This lesson demonstrates how to determine properties of quadrilaterals by using triangles. It is 5 of 5 in the series titled "Using Triangles to Examine Quadrilaterals."
Texas Instruments
Texas Instruments: Investigating Area Relationships
The interactive Cabri Jr. geometry application makes it easy to measure the area of triangles and quadrilaterals. In this activity, students will explore some interesting area relationships in quadrilaterals.
Mangahigh
Mangahigh: Pyramid Panic: Basic Shapes to Advanced Geometry
Guide a mummy safely through the burial chambers of a pyramid as you solve length and area problems in basic to advanced geometry. There are four game zones that deal with circles and triangles, quadrilaterals, the Pythagorean Theorem,...
Government of Alberta
Learn Alberta: Math Interactives: Exploring Shape Classification
Investigate the properties of triangles, quadrilaterals, and regular polygons using this interactive Learn Alberta math resource. Students are able to practice classifying shapes based on their different properties. Be sure to follow the...
Ministerio de Educacion, Cultura y Deporte (Spain)
Cnice: Relacion De Ejercicios Interactivos.
In Spanish. Interactive activities online on various geometric and trigonometric concepts such as area, perimeter, secants, tangents, etc. A terrific resource for students. Site is organized acoording to shape. (triangle, quadrilaterals,...
ClassFlow
Class Flow: Area of Polygons
[Free Registration/Login Required] This flipchart provides students with notes and practice with using formulas for finding the area of triangles and quadrilaterals.
Texas Instruments
Texas Instruments: Tessellations and Tile Patterns
Students understand that a tessellation is covering of a plane with a pattern of figures so there are no overlaps or gaps. They draw quadrilaterals and triangles and explore monohedral, dihedral, and trihedral tessellating patterns.
BBC
Bbc: Bitesize: Maths: 2 D Shapes
Learn about the properties of 2-D shapes: circles, triangles, polygons, and quadrilaterals. Includes information, video, and examples about each, with games and quizzes for reinforcement.
Khan Academy
Khan Academy: Use Pythagorean Theorem to Find Area and Perimeter
Find the area and perimeter of triangles and quadrilaterals by first using the Pythagorean Theorem to find missing side lengths. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video, or...
Ministry of Education and Universities of the Region of Murcia (Spain)
Ministerio De Educacion Y Ciencia: Figuras Geometricas en El Plano
Interactive activities dealing with the areas of quadrilaterals figures.
BBC
Bbc: Area in General
You can pick up some valuable pointers on how to find the area of a triangle, rectangle, and other quadrilaterals. When you finish working your way through the pages you can take an on-line "Test Bite," and check your understanding.
Texas Instruments
Texas Instruments: Measuring Polygons an Introduction to Cabri Jr.
This activity is designed as an introduction to using the Carbri Jr. application on the TI-83+/84+ calculators. Students are guided through the menu system and are shown how to draw triangles, quadrilaterals and and a pentagon. Perimeter...
Geometry Help
Geometry Help: Rectangles
Explains the basic concept of a rectangle with step-by-step instructions and methods for solving specific problems on your own relating to this topic.
The Math League
The Math League: Figures and Polygons
This site provides definitions of different types of polygons and figures.
Geometry Help
Geometry Help: Squares
Explains the basic concept of a square with step-by-step instructions and methods for solving specific problems on your own relating to this topic.
National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Centroid: Center of Gravity
At this site you will find am online discussion about the centroid of a triangle. The page begins with a discussion of observations leading to the centroid of a triangle. Dr. Math explains the correct findings as well as the errors made...
AAA Math
Aaa Math: Geometry
A comprehensive tutorial from AAA Math that contains explanations, interactive practices and challenging games.
ClassFlow
Class Flow: Segments and Polygons
[Free Registration/Login Required] This flipchart reviews segments, parallel and perpendicular lines and then introduces polygons including quadrilaterals. It has many real world examples of shapes and includes Activote assessment.
NumberNut
Number Nut: Shapes, Symbols, and Colors: 2 D Shapes
Did you know that two-dimensional shapes are also called polygons? This lesson describes the various 2-D shapes and includes two interactive games to reinforce skills.
Wolfram Research
Wolfram Math World: Heron's Formula
This site provides a detailed overview of Heron's Formula. Content includes a definition, example, and formula.
Math Is Fun
Math Is Fun: Interior Angles of Polygons
Learn what an interior angle of a polygon is and how you can calculate their value in triangles, quadrilaterals, and pentagons. Includes a chart that overviews the "general rule" for determining the sum of internal angles in any polygon...
National Council of Teachers of Mathematics
Nctm: Illuminations: Angle Sums
Students may use this computer applet to explore angle sums of triangle, quadrilaterals, pentagons and hexagons.
Primary Resources
Primary Resources: 2 D and 3 D Shapes
Here is a huge collection of teacher resources for teaching 2-D and 3-D shapes. Includes smartboard and PowerPoint presentations, as well as worksheets and helpful hints.