Learning About Angle Pairs Formed In Parallel Lines Cut By A Transversal.

Have you noticed that when a transversal cuts two parallel lines; all the acute angles are congruent among them, and all the obtuse angles are congruent among them, and that if you add one acute and one obtuse they are supplementary? Can you identify consecutive interior angles? Or Alternate interior angles? What about corresponding angles?

By working in this lesson, you will clarify your understanding about these angle pairs. The lesson starts by introducing angle pairs using animations and colors; and then it jumps to explain what happens if the lines are parallel. In a very clear way it tells you what angle pairs are congruent, and which ones are supplementary. You will be able to assess your acquired knowledge after most of the examples, by answering a similar problem.

Lesson's Content

Lesson's Glossary

Alternate exterior angles
Exterior angles on alternate sides of the transversal (not on the same parallel line)

Alternate interior angles
Interior angles on alternate sides of the transversal (not on the same parallel line)

Complementary angles
Two positive angles that when added give 90 degrees.

Corresponding angles
Any pair of angles in similar locations with respect to a transversal

Parallel lines
Two lines in the same plane that never cross or intersect.

Perpendicular lines
Two segments, rays, or lines that form a 90 degree angle.

Supplementary angles
Two angles whose measures, when added together, equal 180 degrees.

Transversal
A line that intersects  others.

Vertical angles
Two angles that share a common vertex and whose sides form two straight lines.

Interactive Geometric Applets: Relevant Theorems.

This applet illustrates how angle pairs in parallel lines cut by a transversal keep

their condition of congruence, or how they remain supplementary.

Drag point B between points A and C (Left and Right) and observe the values of the angles.

Do alternate interior, alternate exterior, and corresponding angles remain congruent?

Do same side interior, or consecutive interior angles add 180° to be supplementary?

Vocabulary Puzzle Interactive

Didn't you find what you were looking for? Do your search here!