Unit 2 · Parallel and Perpendicular Lines

2.5Perpendicular Lines

Quick Answer

Perpendicular lines form four right angles. Theorem: if two lines are perpendicular to the same line, they are parallel to each other. The perpendicular from a point to a line is the shortest distance from the point to the line.

Essential Question

What special properties do perpendicular lines have, and how do we use them in proofs and constructions?

Learning Goals

  • 1Apply the definition of perpendicular lines.
  • 2Apply theorems about perpendicular lines.
  • 3Construct a perpendicular from a point to a line.
  • 4Find the distance from a point to a line.

Key Vocabulary

Perpendicular

Meeting at a right angle (90°).

Distance from a point to a line

The length of the perpendicular segment from the point to the line; the shortest distance.

Perpendicular Transversal Theorem

If a transversal is perpendicular to one of two parallel lines, it is perpendicular to the other.

Full lesson content coming soon

Worked examples, guided practice problems, a workbook, quiz, and downloadable PDF resources will be added to this lesson in Phase 2. The learning goals and vocabulary above reflect the complete lesson scope.