College Algebra / Unit 3 Alg 151 short lesson, about 20 seconds
Perpendicular Lines
Captions available
The idea
Perpendicular lines cross at a right angle; their slopes are negative reciprocals, multiplying to −1.
In practice
Slope 2 pairs with slope −1/2: 2 · (−1/2) = −1, a quarter-turn between the lines. Flip the fraction, flip the sign.
Where people slip
Vertical lines break the product rule; their perpendicular is horizontal.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
- Nothing. This is a starting point.
Unlocks
- Nothing yet depends on this.
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