If two non-vertical lines that are in the same plane has the
same slope, then they are said to be parallel. Two parallel lines
won't ever intersect.
If two non-vertical lines in the same plane intersect at a right
angle then they are said to be perpendicular. Horizontal and
vertical lines are perpendicular to each other i.e. the axes of the
Compare the slope of the perpendicular lines
The slope of the red line:
The slope of the blue line
The slopes of two perpendicular lines are negative
The product of the slopes of two perpendicular lines is -1
Videolesson: Are these two line parallel?