What is the definition for perpendicular lines?

Perpendicular lines are lines that intersect at a right angle (90 degrees). Here's a simple way to understand them:

Key characteristics: - They intersect at exactly one point - The angle between them is exactly 90° - They form four right angles at their intersection point - Symbol: ⊥ (for example, line AB ⊥ line CD)

Real-world examples: - The corner of a book - two edges meeting at 90° - Crossroads where streets intersect at right angles - Plus sign (+) - the vertical and horizontal lines are perpendicular - Floor meeting wall in a room

Mathematical properties: - The slopes of two perpendicular lines are negative reciprocals of each other - If line 1 has slope m, line 2 has slope -1/m (in coordinate geometry) - They are the foundation for coordinate systems like the x and y axes

Perpendicular lines are everywhere in geometry, construction, and daily life. They're essential for creating stable structures and accurate measurements. The concept is fundamental from basic geometry through advanced mathematics and engineering!