Perpendicular Lines
This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.
State
Perpendicular lines cross at a right angle; their slopes are negative reciprocals, multiplying to −1.
Show
Slope 2 pairs with slope −1/2: 2 · (−1/2) = −1, a quarter-turn between the lines. Flip the fraction, flip the sign.
Watch for
Vertical lines break the product rule; their perpendicular is horizontal.
Builds on
- Nothing — this is a starting point.
Unlocks
- Nothing yet depends on this.