Learn Before
Definition

Perpendicular Lines

Two lines in a coordinate plane are perpendicular if they intersect at a right angle (9090^\circ). The slopes of perpendicular lines are negative reciprocals of each other: if one line has slope m1m_1 and the other has slope m2m_2, then their product is 1-1, which is written as m1m2=1m_1 \cdot m_2 = -1, or equivalently m1=1m2m_1 = -\frac{1}{m_2}. For example, a line with slope 23\frac{2}{3} is perpendicular to a line with slope 32-\frac{3}{2}, because \frac{2}{3} \left(-\frac{3}{2} ight) = -1. This negative reciprocal relationship does not apply when one of the lines is vertical (with an undefined slope) and the other is horizontal (with a slope of 00); however, a vertical line and a horizontal line are always perpendicular to each other.

0

1

Updated 2026-05-06

Contributors are:

Who are from:

Tags

OpenStax

Elementary Algebra @ OpenStax

Ch.4 Graphs - Elementary Algebra @ OpenStax

Algebra

Math

Prealgebra

Intermediate Algebra @ OpenStax

Ch.3 Graphs and Functions - Intermediate Algebra @ OpenStax

Related
Learn After