Oswego City School District
Regents Exam Prep Center: Theorems and Postulates for Geometry
Here is a partial list of theorems, postulates, and properties.
Mangahigh
Mangahigh: Shape: Recognize Congruent Shapes
Determine whether shapes are congruent or similar.
CK-12 Foundation
Ck 12: Geometry: Triangle Classification Grade 8
[Free Registration/Login may be required to access all resource tools.] Classifying triangles by using angle measures and side lengths.
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.
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.
National Council of Teachers of Mathematics
Nctm: Illuminations: Making Triangles
Understand the mathematical meaning of a triangle and the idea of congruence, or sameness, in geometry.
Science Struck
Science Struck: Similarity Statement in Geometry With Examples
Models how to write a similarity statement about different types of triangles and quadrilaterals.
CK-12 Foundation
Ck 12: Geometry: Aa Similarity
[Free Registration/Login may be required to access all resource tools.] Use the AA Similarity Postulate to determine if triangles are similar.
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.
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.
Khan Academy
Khan Academy: Practice: Determine Similar Triangles: Sss
In this set of questions, students practice identifying side-side-side similarity among triangles. Includes hints.
Khan Academy
Khan Academy: Solve Similar Triangles (Basic)
Given two similar triangles and some of their side lengths, find a missing side length. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
Khan Academy
Khan Academy: Solve Similar Triangles (Advanced)
Given two similar triangles and some of their side lengths, find a missing side length. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
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.
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...
CK-12 Foundation
Ck 12: Geometry: Similarity
[Free Registration/Login may be required to access all resource tools.] Recognize similarity in figures
Jim Loy
Jim Loy's Mathematics Page: Congruence of Triangles
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).
Curated OER
Nova Scotia Dept. Of Education: Mathematics 8: Geometry Diagrams
A collection of diagrams that complement Mathematics 8, a Grade 8 Math text, have been posted here. The diagrams were created using The Geometer's Sketchpad,
CK-12 Foundation
Ck 12: Interactive Geometry: 6.3 Aa Triangle Similarity
If two triangles are similar, it means that all corresponding angle pairs are congruent and all corresponding sides are proportional. However, in order to be sure that two triangles are similar, you do not necessarily need to have...
CK-12 Foundation
Ck 12: Interactive Geometry: 6.5 Sss Triangle Similarity
Explore and understand two triangles that are similar.
CK-12 Foundation
Ck 12: Interactive Geometry: 6.4 Sas Triangle Similarity
Explore and understand triangle 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...
CK-12 Foundation
Ck 12: Geometry: Third Angle Theorem Grades 8 10
[Free Registration/Login may be required to access all resource tools.] Apply the Third Angle Theorem.
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."