2.9 Proving Lines Parallel

Front

What is the definition of parallel lines?

Back

Parallel lines are lines in a plane that never meet; they are always the same distance apart.

Front

What is a transversal in geometry?

Back

A transversal is a line that intersects two or more lines at different points.

Front

What is the Alternate Interior Angles Theorem?

Back

If two parallel lines are cut by a transversal, then each pair of alternate interior angles is congruent.

Front

What is the Converse of the Alternate Interior Angles Theorem?

Back

If two lines are cut by a transversal and the alternate interior angles are congruent, then the lines are parallel.

Front

What are corresponding angles?

Back

Corresponding angles are pairs of angles that are in the same position on different parallel lines cut by a transversal.

Front

What is the Corresponding Angles Postulate?

Back

If two parallel lines are cut by a transversal, then each pair of corresponding angles is congruent.

Front

What is the Consecutive Interior Angles Theorem?

Back

If two parallel lines are cut by a transversal, then each pair of consecutive interior angles is supplementary.

Front

What does it mean for angles to be supplementary?

Back

Two angles are supplementary if the sum of their measures is 180 degrees.

Front

What is the relationship between angles formed by a transversal and parallel lines?

Back

Angles formed by a transversal and parallel lines can be classified as corresponding, alternate interior, alternate exterior, and consecutive interior angles.

Front

How can you prove that two lines are parallel using angle measures?

Back

You can prove that two lines are parallel if you can show that either corresponding angles are congruent, alternate interior angles are congruent, or consecutive interior angles are supplementary.