Geometry · Coordinate Geometry
Perpendicular Slopes
HSG-GPE.B.5
Definition
Perpendicular lines have slopes that are negative reciprocals of each other.
Teach it
Where it is taught, with guided notes, practice, homework, an exit ticket and an interactive Teacher Deck.
Examples
- Slopes of 2 and −1/2 are negative reciprocals, so the lines are perpendicular.
- Slopes of 3 and −1/3 are negative reciprocals, so the lines are perpendicular.
Key rule
Two slopes multiply to −1 exactly when the lines are perpendicular.
Memory hook
Flip and negate the slope to find the perpendicular one.