slopeFor a nonvertical line, slope is the change in y divided by the change in x: y’s change per unit of x. A vertical line has undefined slope.
You’ll leave with these skills
01Tell which slope a parallel line or a perpendicular line needsDistinct nonvertical parallel lines have equal slopes. Nonzero slopes of perpendicular lines are negative reciprocals. Two distinct vertical lines are parallel, and a horizontal line is perpendicular to a vertical line.
02Find a perpendicular line’s slope from the slope you are givenFor a nonzero slope, take its negative reciprocal. A horizontal line instead needs a vertical perpendicular line, whose slope is undefined; a vertical line needs a horizontal one, whose slope is zero.
03Check in Desmos that two lines are perpendicularGraph both lines in Desmos and look for a right angle where they cross.
This lesson is part of the full library
207 lessons that teach every skill the SAT tests
71Math
40Reading
24Grammar
10 full-length practice tests to build test-day stamina and confidence
A Desmos simulator to solve math questions faster
A step-by-step guide to every practice test question
The Bluebook Simulator, so test day feels familiar
A drawing for every key term, so new ideas make sense at a glance
