1. Section 3-4 Parallel and Perpendicular lines.
Michael Schuetz

2. Theorem 3-8: Two Parallel Lines Theorem.If
Then a b c
If two lines are parallel to the same line, then they are parallel to each other.

3. Theorem 3-9: Two Perpendicular Lines Theorem.If
Then t m n
In a plane, if two lines are perpendicular to the same line, then they are parallel to each other.

4. Theorem 3-10: Perpendicular Transversal Theorem.If
Then n l m
In a plane if a line is perpendicular to one of two parallel lines, then it is also perpendicular to the other.

5. t m n Proof of Theorem 3-9: Given: In a plane, Prove: m//n 1 2
Statements
Reasons
1. Given
2. Definition of perpendicular
3. Definition of congruence
4. Converse of Corresponding Angles.

6. Proving a Relationship Between Two Linesc d b a
Given: In a plane,
Prove:
Statements
Reasons
1. Given
2. If two lines are perpendicular to the same line, then they are parallel to each other.
3. If a line is perpendicular to one of two parallel lines, then it is perpendicular to the other.

7. Homework:
P. 167, #’s 8, 10-15, 19-24, 27-32