Lesson: Slopes of Parallel and Perpendicular Lines Mathematics • Third Year of Preparatory School

Students will be able to

• understand that the slope of a line can be related to the angle the line makes with the positive ,
• classify the slope of a line as positive, negative, 0, or infinity when given the (positive or negative) angle the line makes with the positive
  • algebraically,
  • graphically (by visually identifying angles as acute, obtuse, right, or equal to zero),
• find the slope of a line using the the tangent function when given the (positive or negative) angle the line makes with the positive ,
• understand the relationship between the slopes of parallel and perpendicular lines,
• identify whether two given lines are parallel, perpendicular, or neither when given
  • the slopes of the lines,
  • a pair of points that lie on each line,
  • the (positive or negative) angles between the lines and the positive ,
  • a mixture of the above information allowing the slopes of both lines to be found,
• use the relationship between the slopes of parallel and perpendicular lines to find
  • an unknown slope of a line,
  • unknown values in the coordinates of a point that lies on a line,
  • an unknown angle between a line and the positive .