Chapter Three:  
Parallel and Perpendicular Lines

Geometry   Notes

Chapter  3

Section  3.1
Section  3.2
Section  3.3
Section  3.4
Section  3.5
Section  3.6
Section  3.7

Geometry Contents

Take notes on the following topics.

Section 3-2  Proving Lines Parallel

Vocabulary

 Flow Proof (p 123) A proof is a convincing argument that uses deductive reasoning. A proof can be written in many forms.  In a flow proof, arrows show the logical connections between the statements. 

 

Postulate 3-2

If two lines and a transversal form corresponding angles that are congruent, then the two lines are parallel.

Theorem 3-3

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

Theorem 3-4

If two lines and a transversal form same-side interior angles that are supplementary, then the two lines are parallel.

Theorem 3-5

If two lines are parallel to the same line, then they are parallel to each other.

Theorem 3-6

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

Postulate 3-3

If there is a line and a point not on the line, then there exists exactly one line through the point that is parallel to the given line.