ACT Preparation / Unit 9 ACT 0814 short lesson, about 20 seconds
Parallel and Perpendicular Slopes
Captions available
The idea
Parallel lines have equal slopes. Perpendicular lines have slopes that are negative reciprocals, with a product of −1, unless one line is vertical and the other horizontal.
In practice
For slope 2/3, a parallel line also has slope 2/3, and a perpendicular line has slope −3/2.
Where people slip
Negative reciprocal means flip and change the sign; doing only one gives a wrong slope.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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