Math
Parallel and perpendicular lines.
Definition
Parallel lines have the same slope and never intersect. Perpendicular lines intersect at right angles (90°) and have slopes that are negative reciprocals of each other.
Examples
Real-world.
- 1 y = 2x + 1 and y = 2x - 3 are parallel (both have slope 2)
- 2 y = 2x + 1 and y = -½x + 4 are perpendicular (slopes 2 and -½)
- 3 Railroad tracks are parallel lines; a street crossing them is perpendicular
Key Fact
Parallel: m₁ = m₂; Perpendicular: m₁ × m₂ = -1