Illustrative Mathematics
Illustrative Mathematics: G Srt Joining Two Midpoints of Sides of a Triangle
In this task, students must prove that angles and triangles are congruent and that a parallel line passes through the midpoints of two sides of the larger triangle. Aligns with G-SRT.B.4.
Math Open Reference
Math Open Reference: Triangles
A complete reference guide to types of triangles and triangle perimeter and area. It provides definitions and interactive animated activities that enhance further explanation.
Other
Nearpod: Congruent Triangles & Similarity
In this instructional activity on congruent triangles, students explore how to use postulates to identify if triangles are congruent by SSS, SAS, ASA, and AAS.
Geometry Help
Geometry Help: Similar Triangles
Explains the basic concept of similar triangles with step-by-step instructions and methods for solving specific problems on your own relating to this topic.
CK-12 Foundation
Ck 12: Interactive Geometry: 6.7 Applications of Similar Triangles
Learn how similar triangles have congruent corresponding angles and proportional corresponding sides.
Texas Instruments
Texas Instruments: Congruent Triangles
This activity works with a PowerPoint presentation to have students answer questions as to what method a pair of triangles can be proven congruent: SSS, SAS, ASA, AAS, HL.
Analyze Math
Analyze Math: Congruent Triangle Examples
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...
Illustrative Mathematics
Illustrative Mathematics: G Co, G Srt Congruence of Parallelograms
In this task, a student has learned the SSS and SAS congruence tests for triangles and wonders if these tests might work for parallelograms. Aligns with G-CO.C.11 and G-SRT.B.5
Illustrative Mathematics
Illustrative Mathematics: G Gpe, G Co, G Srt Unit Squares and Triangles
In this task, young scholars are shown three unit squares and two line segments connecting two pairs of vertices. They are asked to find the area of a triangle formed by intersecting lines. They can solve it using coordinate geometry or...
National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Congruence and Triangles
This site gives a very thorough explanation of how to tell if two triangles are congruent. Dr. Math explains why SSS, SAS, ASA determine that two triangles are congruent. The Dr. gives a few exercises for the reader to try then gives the...
Sophia Learning
Sophia: Cpctc: Lesson 2
This lesson will demonstrate the use of CPCTC in triangle congruencey proofs. It is 2 of 4 in the series titled "CPCTC."
ClassFlow
Class Flow: Congruence in Triangles
[Free Registration/Login Required] This lesson helps teach congrence in triangles. Includes practice with postulates, theorems, and logical reasoning.
University of Saskatchewan (Canada)
University of Saskatchewan: Triangles
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.
Sonoma State University
Sonoma State University: Parallel Lines and Similar and Congruent Triangles
This site defines eleven theorems relating to parallel lines and similar and congruent triangles. Links to the theorems and relevant term descriptions are provided.
Illustrative Mathematics
Illustrative Mathematics: G Srt, G Mg How Far Is the Horizon?
Some friends are at the beach looking out onto the ocean on a clear day and they wonder how far away the horizon is. A second problem asks how far the horizon would be from the top of a mountain. Students must also answer a question...
CK-12 Foundation
Ck 12: Geometry: Aa Similarity (Intermediate)
[Free Registration/Login may be required to access all resource tools.] This concept teaches students how to identify whether or not two triangles are similar using AA Similarity.
CK-12 Foundation
Ck 12: Geometry: Perimeter and Area Study Guide
[Free Registration/Login may be required to access all resource tools.] This study guide looks at the definitions and units for perimeter, area, and circumference, and at the perimeter and area of different shapes, including regular...
Geometry Help
Geometry Help: Tangent Lines
Explains the basic concept of congruent triangles with step-by-step instructions and methods for solving specific problems on your own relating to this topic.
Khan Academy
Khan Academy: Proofs With Transformations
Explore different ways of proving some theorems about lines and angles. Some transformations are used.
Illustrative Mathematics
Illustrative Mathematics: 8.g, G Gpe, G Srt, G Co Is This a Rectangle?
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.
Sophia Learning
Sophia: Corresponding Parts: Lesson 5
This lesson will define the phrase corresponding parts (e.g. angles, sides, etc.). It is 5 of 5 in the series titled "Corresponding Parts."