When two lines intersect forming a right (90 degree) angle, geometers label that angle using a square so that it is clear that it is a special angle, a right angle. See the diagram below.[br][br]Use the MOVE tool [icon]/images/ggb/toolbar/mode_move.png[/icon]to move the [b]Drag Points[/b] of the two intersecting lines.[br][br]Try to orient the lines so that there is a right angle at their intersection.[br][br]Now drag the lines again and try to find other combinations that form a right angle at the intersection.[br][br]Once you have formed a right angle at the intersection of the two lines, what do you notice about all four of the angles formed?[br][br]When two intersecting lines or line segments form a right angle, the two lines or line segments are said to be [b][i][color=#ff0000]perpendicular[/color][/i][/b].