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
coordinate plane.
Example:
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
reciprocals.
The product of the slopes of two perpendicular lines is -1
since
Videolesson: Are these two line parallel?
