[Free Registration/Login may be required to access all resource tools.] This study guide reviews terminology for triangles, triangle properties, different types of triangles, and interior and exterior angle theorems.

[Free Registration/Login may be required to access all resource tools.] This study guide reviews the formulas for area and perimeter of triangles and different kinds of quadrilaterals.

Explore the world of congruent triangles in this mini-lesson. Provides a definition and examples that help with understanding their properties. Includes a short video and practice questions with answers.

Learn about the types of triangles by taking a look at an example and a video lesson.

This site from the University of California deals with different applications and topics pertaining to triangles, particularly triangulation.

In this instructional activity, students learn to classify triangles by the size of the angles and the measures of the sides. Students will use interactives to explore equilateral, isosceles, scalene, acute, obtuse, and right triangles....

Learn about the 30-60-90 triangle with this helpful reference tool. Provides a detailed definition, examples, and an interactive activity that enhances further explanation. Includes links to related topics.

Use your knowledge of 30-60-90 and 45-45-90 triangles to solve some problems.

This lesson plan provides students with an opportunity to practice drawing and measuring triangles and angles. It also shows pictures and gives definitions of each type of angle and triangle.

Discover some theorems about triangles.

Learn how to sine to find the area of a triangle.

Explore applications of triangle theorems.

Find out about some common centers of triangles.

Take this ten question quiz on right triangles as a review for a quiz or test. After submitting your results, you will get step by step instructions for each problem.

A reference guide to obtuse triangles. It provides a definition and interactive animated activity that enhances further explanation.

Explore acute triangles with this handy reference guide. Provides a detailed definition and an interactive activity that enhances further explanation. Includes links to related topics.

This site from the University of Saskatchewan provides an explanation of similar triangles, the Pythagorean theorem, and the distance between arbitrary points in a plane. Example problems for each of these concepts are provided.

Find explanations of the ways to prove triangles are congruent. There is a link for Congruence Of Triangles, Part II to find the proofs of some ways to prove congruence of triangles from other postulates (i.e. Assume SAS prove ASA).

Learn how to find the areas and perimeters of triangles and special quadrilaterals.

Plans for building a 3-D triangle with seemingly impossible structure. Good for projects and presentations.

This is the second version of a task asking students to find the areas of triangles that have the same base and height. This presentation is more abstract as students are not using physical models. They still determine the area of each...

Students are taught how to make a sundial. The relationship between angles and the sides of a right triangle are explored. Great lesson plan ideas with plenty of background information. The lesson is adapted for grade levels k-6 with...

Explore finding and measuring perimeter of figures.

Learn about states of matter on a flight tour over the Atlantic Ocean.