Explore The Slopes of lines that are parallel and Perpendicular to a given line (in red). [br]Click Show Parallel or Show Perpendicular to get started. [br]Drag the two original blue points to create a new starting line. (Drag point D to move the parallel line.)

Parallel Line: Create a few lines through two given points. [br]Note the slopes of the original lines, and the slopes of the Parallel Lines.[br]What do you notice about the slopes?[br]Think of a rule that parallel lines have to follow. [br][br]Perpendicular lines: Create a few lines through two given points. [br]Note the slopes of the original lines and the slopes of the Perpendicular lines. [br]What do you notice about the slopes?[br]Think of a rule that perpendicular lines have to follow.