Slopes of Perpendicular Lines The purpose of this activity is to explore the relationships of the slopes of perpendicular lines. Lines a and b have been constructed to be perpendicular. Use point B to drag the shape. Perpendicular Lines 1) How do you know these lines are perpendicular? 2) What is the slope of line a? Why? 3) What is the slope of line b? Why? 4) Click point B and drag it to (0, 2) on the coordinate plane. What do you notice about the slopes? 5) Now drag point B to (0, -4) on the coordinate plane. What do you notice about the slopes? 6) Take a few minutes to drag point B to any point on the coordinate plane. Form a conjecture about the slopes of perpendicular lines.