Discusses the different types of triangles and their angles. [6:00]

Khan Academy learning modules include a Community space where users can ask questions and seek help from community members. Educators should consult with their Technology administrators to determine the use of Khan Academy learning modules in their classroom. Please review materials from external sites before sharing with students.

This video lesson describes and provides examples of right, acute, and obtuse triangles. Students can check their understanding with an assessment. [2:24]

This video lesson shows examples of classifying triangles by their angle measurements. Students can check their understanding with an assessment. [3:54]

Explains how to classify a triangle just by knowing the angle sizes. [5:30]

Khan Academy learning modules include a Community space where users can ask questions and seek help from community members. Educators should consult with their Technology administrators to determine the use of Khan Academy learning modules in their classroom. Please review materials from external sites before sharing with students.

This lesson [2:00] will define the phrase corresponding parts (e.g. angles, sides, etc.). It is 1 of 5 in the series titled "Corresponding Parts."

This lesson [4:27] will define the phrase corresponding parts (e.g. angles, sides, etc.). It is 2 of 5 in the series titled "Corresponding Parts."

Congruent triangles are investigated in this video lesson. The tutorial demonstrates how to use four tricks to determine if triangles are congruent. Students can check their understanding with an assessment. [5:27]

This video tutorial describes four ways to determine if two triangles are congruent. Students can check their understanding with an assessment. [5:40]

A structured geometry program teacher edition of daily lesson plans and teacher supports to accompany the College Access Reader: Geometry student edition.

Features a definition and a video lesson on congruent triangles with examples. [1:11]

CK-12 Foundation's Geometry FlexBook is a clear presentation of the essentials of geometry for the high school student. Topics include: Proof, Congruent Triangles, Quadrilaterals, Similarity, Perimeter & Area, Volume, and Transformations.

Explains the basic concept of the perimeter of geometric shapes with step-by-step instructions and methods for solving specific problems on your own relating to this topic.

Explains the basic concept of triangles with step-by-step instructions and methods for solving specific problems on your own relating to this topic.

Just as rigid motions are used to define congruence in Module 1, so dilations are added to define similarity in Module 2.  To be able to discuss similarity, students must first have a clear understanding of how dilations behave.  This is done in two parts, by studying how dilations yield scale drawings and reasoning why the properties of dilations must be true. Once dilations are clearly established, similarity transformations are defined and length and angle relationships are examined, yielding triangle similarity criteria.  An in-depth look at similarity within right triangles follows, and finally the module ends with a study of right triangle trigonometry.

Find the rest of the EngageNY Mathematics resources at https://archive.org/details/engageny-mathematics.

Resource examines the area of geometric solids through examples and a video lesson. [0:39]

CK-12's Geometry - Second Edition is a clear presentation of the essentials of geometry for the high school student. Topics include: Proofs, Triangles, Quadrilaterals, Similarity, Perimeter & Area, Volume, and Transformations.

CK-12's Texas Instruments Geometry Student Edition Flexbook is a useful collection of exercises intended to enrich a student's understanding of basic geometric principles.

CK-12's Texas Instruments Geometry Teachers Edition Flexbook is a useful collection of exercises intended to enrich a student's understanding of basic geometric principles.

CK-12 Geometry Teacher's Edition covers tips, common errors, enrichment, differentiated instruction and problem solving for teaching CK-12 Geometry Student Edition. The solution and assessment guides are available upon request.