Parallel Lines

In this section, we learn how to determine if we have parallel or perpendicular lines. Parallel lines are any two lines on a plane that will never intersect. They will have the same slope, but different y-intercepts. To determine if we have parallel lines, place each line in slope-intercept form and inspect the slope and y-intercept. If the two lines have the same slope, but a different y-intercept, they are parallel lines. Perpendicular lines will intersect at a 90-degree angle. When we have perpendicular lines, they have a property such that the product of their slopes is (-1). To determine if we have perpendicular lines, place each line in slope-intercept form and copy the slope in each case. We then look to see if the product of the two slopes is (-1). If the product is (-1), we have perpendicular lines.