Parallel & Perpendicular Lines
Perpendicular Lines
By definition, two lines are perpendicular if they intersect at right angles. Two lines with slopes m1 and m2 are perpendicular if . In other words the slopes of perpendicular lines are the opposite reciprocals of each other. For example, if the slope of a line is , then the slope of a line perpendicular to it is . Using this property of the slopes of perpendicular lines, an equation of a line perpendicular to a given line can be written.