Parallel & Perpendicular Lines

A Brief Overview

Parallel Lineshave the SAME

SLOPE & DIFFERENT

Y-INTERCEPTS

In this example, both lines A & B have slopes equal to 1/2The lines cross the y-axis in different placesThe lines are PARALLEL

In this example, the lines appear to be parallel, but actually have different slopes. The lines are NOT PARALLEL

PERPENDICULAR LINES

have OPPOSITE RECIPROCAL slopesThis means that the sign of the slopes are reversed and

the slopes, when written as a fraction, are flipped

**if you multiply the slopes of perpendicular lines, the answer will be -1 with the exception of a vertical line and

a horizontal line

Examples of opposite reciprocal slopes:

-3 44 3

& 0 & Undefined 1 -22

&

Line A has a slope of 2/3

Line B has a slope of -3/2

2/3 & -3/2 are opposite reciprocals, the lines are perpendicular

Line A has a slope of 4/3

Line B has a slope of -3/5

4/3 & -3/5 are NOT opposite reciprocals, the lines are NOT PERPENDICULAR