Parallel Line Theorem Teacher Resources

Lead your class on an exciting journey through the world of math as they review geometry facts and solve for unknown angles. They learn how to use auxiliary lines and congruent angles to correctly complete each practice problem...

Geometric figures are perfect to use for proofs. Scholars prove conjectures about whether given points lie on a triangle and about midpoints. They use a provided dialogue among fictional students to frame their responses.

This task asks learners to prove that the segment joining the midpoints of two sides of a parallelogram is both congruent and parallel to an adjacent side of the parallelogram. The activity would be good to use in a discussion about how...

Young scholars explore differents types of triangles and quadriaterals. In this polygon instructional activity, students  model identify and compare two and three dimensional geometric figures. Young scholars create tangrams and...

In this word worksheet, 9th graders examine pictures and write a mathematical phrase to describe the picture.  This one-page worksheet contains 25 problems.  Answers are provided.

Students explore the concept of polygon properties. In this polygon properties lesson, students draw polygons with different numbers of sides such as pentagons, octagons, hexagons, etc. Students identify different geometric shapes in the...

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

[Free Registration/Login may be required to access all resource tools.] This concept teaches students how to use the Triangle Proportionality Theorem with multiple parallel lines.

In this activity, students will explore the proportional relationships involved in multiple parallel lines being cut by transversals. These relationships are approached through exploration of a sail design problem, where students are to...

Use this site to learn about the fourth locus theorem regarding parallel lines. Click on the "Topic Index" link to find related practice activities and resources.

Demonstrates how to use the triangle sum theorem, properties of isosceles triangles, and special angle pairs formed when parallel lines are cut by a transversal to set up an equation using given algebraic expressions for angle measures...

[Free Registration/Login may be required to access all resource tools.] In this lesson students find the distance between two parallel lines. Students examine guided notes, review guided practice, watch instructional videos and attempt...

This video demonstrates how to use the triangle sum theorem, properties of isosceles triangles, and special angle pairs formed when parallel lines are cut by a transversal to set up an equation using given algebraic expressions for angle...

[Free Registration/Login may be required to access all resource tools.] This concept teaches students how to use the Triangle Proportionality Theorem with multiple parallel lines.

Identifies which angles are congruent when parallel lines are cut by a transversal. [7:07]

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

This video tutorial demonstrates solutions to problems #51-55 of the California Geometry released state test questions. Problems address proving and using the Pythagorean theorem and compass constructions. [12:35]

Consider two parallel lines that are intersected by a transversal, and when it crosses the two others, many different angle pairs are formed. See the special properties of the angle pairs in this interactive.

A wealth of resources for teachers introducing locus theorems to students. Lessons cover simple definitions, provide examples and diagrams, and offer connections to real-life situations. Practice exercises offer students online quizzes...

Solving for measures of the angles in a triangle using algebra, the triangle sum theorem, and properties of angles created by a transversal that cuts parallel lines. [6:05]

Proof that the sum of the angles in a triangle is 180 using the relationship of angles formed when parallel lines are cut by a transversal. This video also appears in the Geometry: Triangles strand. [6:31]

[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.

This study guide on lines and angles covers key terminology; line notation; parallel, perpendicular, and skew lines; and postulates and theorems about lines. It is available for download with free registration.