What is the Cartesian Coordinate System?

The Cartesian Coordinate System is a way to locate points on a plane using numbers.

It uses:
• a horizontal number line called the x-axis
• a vertical number line called the y-axis

These two axes cross at the origin, which is (0,0).

Ordered pairs

A point is written as an ordered pair:

(x, y)

x = horizontal movement
y = vertical movement

Example:
(3, 2) means move 3 units right and 2 units up.

Quadrants

The coordinate plane is divided into four quadrants:

Quadrant I: x positive, y positive
Quadrant II: x negative, y positive
Quadrant III: x negative, y negative
Quadrant IV: x positive, y negative

Why the coordinate system matters

It allows us to:
• graph equations
• visualize functions
• compare relationships