Explore different ways of proving some theorems about lines and angles. Some transformations are used. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video, or receive hints.

In this exercise, students practice classifying shapes by line and angle types. Students receive immediate feedback and have the opportunity to get hints and try questions repeatedly.

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

Try these three problems about finding the measures of different angles that arise from diagrams involving parallel lines and transversals. Detailed solutions are written out for these three problems of moderate difficulty.

Angles, parallel lines, and transversals are explained through examples and a video lesson. [1:01]

Explains the terms and symbols used to discuss line angles, what an angle is, and the types of angles. Includes short video lesson demonstrating how to use a protractor to measure an angle. [0:57]

Study inscribed angles in semicircles and quarter-circles. What conjectures can you make about the measure of an inscribed angle in semi- or quarter-circles?

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

Read a description of intersecting lines and all about the different kinds of angles they form. Includes examples.

[Free Registration/Login may be required to access all resource tools.] Identifying types of lines as parallel lines, perpendicular lines or intersecting lines.

A list of geometry definitions and a matching activity.

[Free Registration/Login may be required to access all resource tools.] Apply the definitions of midpoint, segment bisector, and angle bisector.

[Free Registration/Login Required] Explore the relationships between parallel lines and the rules of angle measurements.

[Free Registration/Login Required] This flipchart regards parallel lines and relationship of angles created by a transversal. Includes lesson on vocabulary, Jeopardy-style game, and quiz.

[Free Registration/Login may be required to access all resource tools.] Use alternate interior angles to determine angle congruency and the presence of parallel lines.

[Free Registration/Login may be required to access all resource tools.] Use alternate exterior angles to determine congruency and the presence of parallel lines.

[Free Registration/Login may be required to access all resource tools.] This concept introduces students to alternate exterior angles and how to use them to determine whether or not lines are parallel.

Provides an introduction to geometry with definitions of points, lines, planes and angles through the use of examples and a brief video lesson. [1:28]

Find missing angles given two parallel lines and a transversal. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video, or receive hints.

This site provides a step-by-step method to construct congruent segments and angles with a straight edge and compass.

This site defines parallel lines, parallel lines cut by a transverse, and congruent triangles. It also contains links for related terms.

Material to supplement classroom instruction on parallel lines: a lesson on angles with parallel lines, a practice quiz, and a link to an investigation on angles with parallel and non-parallel lines.

[Free Registration/Login may be required to access all resource tools.] Identify adjacent and vertical angles formed by intersecting lines and then find missing angle measures.

[Free Registration/Login may be required to access all resource tools.] Identify adjacent and vertical angles formed by intersecting lines and then find missing angle measures.