Angle B is given and line c is the angle bisector of this angle (the red line). A point D is on the angle bisector. DE and DF are perpendicular to the sides of the angle. [list] [*] Move D on the angle segment. What do you notice about the measure of DF and DE? [*] You can check the box next to "The measure of DF and DF" to see the measure of these two segments. [*] Can you form a conjecture? [*] You can change the measure of angle B by moving the point on the slide. Does your conjecture hold? [/list]