Merriam-Webster
Merriam Webster: Dictionary Illustration: Types of Triangles
A labeled illustration of six different types of triangles.
Doina Popovici
Math Play: Classifying Triangles
Practice identifying triangles as either acute, right, or obtuse in this interactive game.
Sophia Learning
Sophia: Triangle Height: Lesson 2
This lesson will demonstrate how to locate the height in an obtuse, right, and acute triangle. It is 2 of 5 in the series titled "Triangle Height."
Sophia Learning
Sophia: Triangle Height: Lesson 4
This lesson will demonstrate how to locate the height in an obtuse, right, and acute triangle. It is 4 of 5 in the series titled "Triangle Height."
Oswego City School District
Regents Exam Prep Center: Triangle Information
This Oswego City School District site from the Regents Exam Prep Center provides an explanation of the classifications of triangles both by sides and by angles. Pictures are also included.
Wolfram Research
Wolfram Math World: Cut the Knot! Angles
Very good site with links to reviews of various angles.
Rice University
Rice University: Geometry Online: Impossible Triangles
This site has an activity that displays several impossible triangles. The rules for triangles are also displayed. The student has to determine which rule has been violated for each impossible triangle.
University of Georgia
University of Georgia: Inter Math: Altitude of a Triangle
This site gives a description along with a visual representation of the altitude of a triangle. There are links to related terms, everyday examples, challenging problems, more information, and the interactive check point involving...
Illustrative Mathematics
Illustrative Mathematics: G Co Classifying Triangles
The goal of this task is to help students synthesize their knowledge of triangles where only two of the vertices have been given. They will need to know that a triangle inscribed in a circle, with a diameter of the circle as one side, is...
Beacon Learning Center
Beacon Learning Center: Anglemania!
Students explore four types of angles in this interactive web lesson.
Mocomi & Anibrain Digital Technologies
Mocomi: Types of Triangles
Explore the different types of triangles and other properties.
ClassFlow
Class Flow: Classifying Triangles
[Free Registration/Login Required] This lesson covers methods of classifying triangles, both according to the length of their sides and by the measure of their interior angle.
University of Saskatchewan (Canada)
University of Saskatchewan: Trigonometric Functions
This site examines the six trigonometric functions from a right triangle point of view. Provides information, examples, and lots of exercises for understanding.
Oswego City School District
Regents Exam Prep Center: Geometry Vocabulary Resources
A list of geometry definitions and a matching activity.
University of Georgia
University of Georgia: Inter Math: Oblique
This site describes the concept of oblique, expressing both triangles and three dimensional solids. Be sure to use the links to related terms, everyday examples, challenging problems, more information, and the interactive check point...
Quia
Quia: Geometric Terms Word Search
Do you need practice remembering or learning different geometry vocabulary words and definitions? This word search is the web site for you! There is a link to a list of terms with definitions you can click if you want to see if you are...
The Math League
The Math League: Figures and Polygons
This site provides definitions of different types of polygons and figures.
Windstream
Ojk's Precalculus Study Page: The Law of Cosines
An introduction to solving acute and obtuse triangles by using the law of cosines, including a derivation of the formula. Includes several pistures and examples.
Windstream
Ojk's Precalculus Study Page: The Law of Sines
An introduction to solving acute and obtuse triangles by using the law of sines, including a derivation of the formula. Includes several pictures and examples.
The Math League
The Math League: Figures and Polygons
This website has basic definitions for most polygons, regular and irregular.