Parallel & Perpendicular Lines
Section: Coordinate GeometryBank code: COG-PPLGRE frequency: Medium-HighPro
1. Core Idea
Two rules, and they are the whole topic:
- Parallel lines have equal slopes. m1 = m2
- Perpendicular lines have slopes whose product is -1. m1 x m2 = -1
The second is more usefully remembered as: flip the fraction and change the sign (the "negative reciprocal").
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