Theorems About Parallel Lines (3-5 to 3-10)

Question 1

What is Theorem 3-5?

Answer 1

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

This is the true converse of Theorem 3-2.

Question 2

What is Theorem 3-6?

Answer 2

If two lines are cut by a transversal and same side interior angles are supplementary then the lines are parallel.

This is the true converse of Theorem 3-3!

Question 3

What is Theorem 3-7?

Answer 3

In a plane, two lines perpendicular to the same line are parallel.

Question 4

What is Theorem 3-8?

Answer 4

Through a point outside a line, there is exactly one line parallel to the given line.

It means a line is unique.

Question 5

What is Theorem 3-9?

Answer 5

Through a point outside a line there is exactly one line perpendicular to the given line.

Question 6

What is Theorem 3-10?

Answer 6

Two lines parallel to a third line are parallel to each other (both coplanar or in space).