[Free Registration/Login Required] Students are given triangles and angles and are to determine which triangles are congruent. Click learn more to watch a video and challenge me to try a practice question.

This site defines eleven theorems relating to parallel lines and similar and congruent triangles. Links to the theorems and relevant term descriptions are provided.

Use this calculator to find the unknown angles in a right triangle using the Pythagorean Theorem. Once you know the sides you can calculate the perimeter, semiperimeter, area, and the altitudes.

In this lesson, students learn how to inscribe a square in a circle. Aligns with G-CO.D.13

ThatQuiz is an excellent assessment tool for teachers and students. At this site, teachers can create individualized or group assessments on a variety of math topics. Students take these practice assessments directly online and receive...

On this site, there are several math problems to explore and solve. Look through some solutions by famous mathematicians and expand your thinking about some interesting math concepts. Teachers of elementary grades may want to use this...

A thorough look at the extensive uses of geoboards in the classroom. Links are listed which give introductory information on geoboards - for teachers new to using them. Then, lesson plans are provided for using geoboards in teaching...

This University of St. Andrews site contains a brief overview of this mathematician's accomplishments.

For this task, students are given four sets of coordinate pairs and are asked to determine if they represent a rectangle. Aligns with 8.G.A, 8.G.B, G-CO.B, G-GPE.B, and G-SRT.B.5.

This activity is designed to give learners practice with the properties of special quadrilaterals (parallelograms, rectangles, rhombuses, squares, trapezoids, and kites). The students are provided with a "murder mystery" sheet with...

The purpose of this lesson is to help students apply math concepts concerning similar triangles and trigonometric functions to real life situations. The students learn how to take these concepts and use them to find measurements of...

Material to supplement classroom instruction on mean proportional in a right triangle: a lesson with a definition of "mean proportional" as well as theorems with examples; an online multiple-choice quiz with answers; and guidelines for...

This lesson expands your knowledge about circles by learning about the segment of a circle, which will include its mathematical definition, area of the segment, types of segments in a circle, theorems based on a segment of a circle, and...

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?"...

This is an inquiry lesson used to review Algebra 1 objectives by applying them to geometry concepts. Students explore the properties of quadrilaterals and classify them by definition. This lesson can be use in geometry classes. Students...

[Free Registration/Login Required] Flipchart walks through the lesson on Proportions and similarity, as well as some of the theorems that support the concept.

Loci are applied to word problems in this online tutorial. Practice problems are included. The teacher resource page supplies practical problems.

Discover the world of "similarity" in this test prep tutorial on similar triangles. Detailed explanation of concept with examples, challenging interactive practice, and a classroom activity that integrates math and science.

In this lesson, learn all about the 30-60-90 triangle. Learn about its sides, its area, and the rules that apply to these triangles. Includes simulations and practice questions.

Dr. Math gives a student a hint on how to prove that an inscribed angle is equal to 1/2 the central angle. You should know what the central angle and inscribed angle are to utilize this site.

The geometry tutorial investigates similar triangles. Students learn about the definitions and theorems of similar triangles. Topics included are angle-angle, side-side-side, and side-angle-side similarity. The activity has several...

The geometry tutorial investigates the definitions and theorems related to inscribed and central angles in circles. An example with a detailed solution is included.

The geometry tutorial investigates congruent triangles. Students learn about the definitions and theorems on congruent triangles. Some topics included are angle-side-angle, side-side-side, and side-angle-side congruence postulates. The...

Use the triangle congruence criteria SSS, SAS, ASA, and AAS to determine that two triangles are congruent. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.