Student Learning Objectives
Name:_______________________________Block:___________
4.9 Slopes of Parallel and Perpendicular Lines
Standard: CC.9-12.G.GPE.5 Prove the slope criteria for parallel lines and use them to solve geometric problems (e.g., find the
equation of a line parallel or perpendicular to a given line that passes through a given point). Also CC.9-12.F.IF.7
I can…
I can identify and graph parallel and perpendicular lines.
I can write equations to describe lines parallel or perpendicular to a given line.
Definitions
Parallel Lines:
Perpendicular Lines:
Copy down “Know it! Note” page 293.
Parallel Lines
Words
Graph
Copy down “Know it! Note” page 295.
Perpendicular Lines
Words
Graph
IN OTHER WORDS…IDENTIFY THE SLOPE


If the linear equations have the same SLOPE = PARALLEL LINES
If the linear equations have the opposite sign and is the reciprocal = PERPENDICULAR
Identify which two lines are parallel.
PARALLEL LINES:
Identify which two lines are perpendicular.
PERPENDICULAR LINES:
GET YOUR DUCKS IN A ROW
1. All equations must be in slope-intercept form!!!!
Look at their SLOPES (the number with X or X’s Best friend)
3. Three OPTIONS from here
 Same SLOPES = PARALLEL LINES
 Opposite sign and it’s the reciprocal = PERPENDICULAR LINES
 Not the same = NEITHER nothing special just another line :0(
2.
WRITING PARALLEL LINES
IN SLOPE-INTERCEPT FORM
WRITING PERPENDICULAR LINES
IN SLOPE-INTERCEPT FORM