Parallel lines are lines that do not intersect. They are shown as lines AB and CD that never meet. Perpendicular lines intersect to form a right angle, as shown with lines m and n. Angles that are opposite each other across a straight line, like angles 1 and 4, are called vertically opposite angles and are equal.

1. LINES AND
ANGLES

2.  Def: line that do not intersect each other are
called parallel lines.
 Illustration: B
A D
l
m C
 Notation: l || m AB || CD

3. Examples of Parallel Lines
• Hardwood Floor
• Opposite sides of windows, desks, etc.
• Parking slots in parking lot
• Parallel Parking
• Streets: Laramie & LeClaire

4. Examples of Parallel Lines
• Streets: Belmont & School

5.  Def: Lines that intersect to form a right angle are
called pependicular linese.
m
 Illustration:
n
 Notation: m n
 Key Fact: 4 right angles are formed.

6. Ex. of Perpendicular Lines
• Window panes
• Streets: Belmont and Cicero

7.  Def: a line that intersects two lines at different
points
t
 Illustration:

8.  Two angles that are opposite to each other
are called vertically opposite angles.
t
1 4
1 2
3 4
2 3
5 6 5 8
7 8 6 7

9.  Two angles that form a line (sum=180 )
t
1+ 2=180 5+ 6=180
1 2
2+ 4=180 3 4
6+ 8=180
4+ 3=180 5 6
8+ 7=180
3+ 1=180 7 8 7+ 5=180

10.  A line segment has two end points.
 A ray has only one end point.
 A line has no end points on either side
 An angle is formed when two lines meet.
 A transversal is a line that intersect two or
more lines at distinct points
 The various angles formed by a transversal are
1. Adjacent angles
2. Corresponding angles
3. Vertically opposite angles alternate angles
4. Linear pair