1. Intro to Parallel Lines
Notes 4.5
Intro to Parallel Lines

2. Plane
a surface such that if any two points on the surface are connected by a line, all points of the line are also on the plane.
Coplanar – lie on the same plane.
Noncoplanar – Do not lie on the same plane.

3. PARALLEL LINES l Definition: lines that do not intersect.
Notation: l || m AB || CD A B C D l m

4. PERPENDICULAR LINES m n
Def: Lines that intersect to form a right angle.
Notation: m  n
Key Fact: 4 right angles are formed. m n

5. Transversal A line that intersects 2 lines at 2 different points .
Forms 8 different angles. 1 2 3 4 6 5 7 8

6. Vertical Angles
∠1 & ∠ 3
∠2 & ∠ 4
∠5 & ∠ 7
∠6 & ∠ 8

7. Linear Pairs – 2 angles that make a line
∠1 & ∠ 2
∠1 & ∠ 4
∠2 & ∠ 3
∠3 & ∠ 4
∠5 & ∠ 6
∠6 & ∠ 7
∠7 & ∠ 8
∠5 & ∠ 8

8. Corresponding Angles ∠1 & ∠ 5 ∠2 & ∠ 6 ∠3 & ∠ 7 ∠4 & ∠ 8
(Same place on different line)
∠1 & ∠ 5
∠2 & ∠ 6
∠3 & ∠ 7
∠4 & ∠ 8

9. Alternate Interior Angles
∠3 & ∠ 5
∠4 & ∠ 6

10. Alternate Exterior Angles
∠1 & ∠ 7
∠2 & ∠ 8

11. Same Side Interior Angles
Consecutive Interior Angles
∠3 & ∠ 6
∠4 & ∠ 5