This site contains a comprehensive study of triangle centers. Seems more for an advanced level. Provides a list of six links to 1114 centers.

Explore the triangle inequality theorem with this helpful reference tool. Provides a detailed definition and an interactive activity that enhances further explanation. Includes links to related topics.

Students learn about trigonometry, geometry and measurements while participating in a hands-on interaction with LEGO MINDSTORMS NXT technology. First they review fundamental geometrical and trigonometric concepts. Then, they estimate the...

[Free Registration/Login may be required to access all resource tools.] Use the Pythagorean Theorem to determine if triangles are acute, obtuse, or right triangles.

A description of the legs of a triangle is provided along with a visual representation. Be sure to follow the links to related terms, everyday examples, challenging problems, more information, and the interactive check-point involving...

Explore finding and measuring perimeter of figures.

In order to use this source to assess students' historical thinking skills, students should understand the history of industrialization and the working conditions typical of late nineteenth-century factories. Students will analyze...

Explains mean proportionals (or geometric means) by providing theorems and examples.

This lesson will demonstrate the use of CPCTC in triangle congruencey proofs. It is 2 of 4 in the series titled "CPCTC."

Finding the third angle of a triangle becomes easier by the explanation and examples presented.

Article discusses the impact that the Triangle Company fire had on labor laws and unions.

An interesting approach to how to analyze a speech. Presents a rhetorical pentangle as well as a rhetorical triangle, where each of the vertices represents an item to analyze. There is also an outline of the different areas to examine in...

[Free Registration/Login may be required to access all resource tools.] Use Law of Cosines and Law of Sines in different triangle situations.

There are many other sequences that are based on certain geometric shapes. These sequences are often called Figurate numbers, numbers that can be represented using geometric shapes. Examples include square, triangle, and tetrahedral...

Explore this course in sequences and patterns including simple sequence, triangle and square numbers, terms, recursive formulas, and explicit formulas. Click on Trailer on the top left to watch an introductory video.

This section explores the Pythagorean Identity and how it applies to right triangles set inside unit circles, in terms of sine, cosine, and tangent functions.

The introduction of this lesson has students verifying the famous Pythagorean Theorem with a hands-on proof. Students will then apply the Theorem in one of two ways: by solving for the side lengths of a right triangle and by determining...

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.

Here is a site that clearly and thoroughly explains the Pythagorean Theorem from solving for missing sides of a right triangle through its proof. There are example problems solved, problems for the student to attempt, and answers to the...

A comprehensive list of 2D shapes and 3D solids with everything from a triangle to a dodecahedron. Includes illustrations and short descriptions of attributes for each.

Activities in this lesson explore how to identify the coordinates where special right triangles intersect with the unit circle in all four quadrants, use both degrees and radians to identify angles, and explore angles of different sizes...

You can pick up some valuable pointers on how to apply the Pythagorean Theorem here. When you finish working your way through the pages you can take an on-line "Test Bite," and check your understanding.

[Free Registration/Login may be required to access all resource tools.] Apply the Midsegment Theorem.

This site from the Pennsylvania State University provides a hands-on activity to bridge the gap between right triangles, 30-60-90 and 45-45-90 theorems, and trigonometry, and what every student wants to know, "When will I ever use this?"...