Perpendicular lines

Definition

Perpendicular lines are two lines that intersect at a right angle (90 degrees). They are a fundamental concept in geometry and are essential for defining orthogonality in various geometric contexts.

5 Must Know Facts For Your Next Test

1. Perpendicular lines intersect to form four right angles.
2. The slope of one perpendicular line is the negative reciprocal of the slope of the other.
3. In a coordinate plane, if line A has a slope of m, then a line perpendicular to it will have a slope of -1/m.
4. Perpendicularity is denoted with the symbol ⊥ (e.g., AB ⊥ CD).
5. When constructing perpendicular lines from a point on or off the line, various methods such as using a protractor or compass can be applied.

Review Questions

• What angle is formed at the intersection of two perpendicular lines?
• If one line has a slope of 3, what is the slope of a line perpendicular to it?
• How can you denote that two lines are perpendicular in notation?

Related terms

Parallel Lines: Lines in the same plane that never intersect and are equidistant from each other.

Right Angle: An angle that measures exactly 90 degrees and is formed by perpendicular lines.

Slope: A measure of the steepness or inclination of a line, usually represented as rise over run.