If two lines are perpendicular with respect to each other, then the product of their slopes is equal to .
Two lines are respectively perpendicular to two parallel lines Show that they are parallel to each other.
When two lines of slopes m1 & m2 are perpendicular to each other. Product of their slopes is 1
If the slopes of two lines are equal, then the lines are __ to each other.
Two non-vertical lines are perpendicular if and only if the product of their slopes is 1.