# Cartesian plane

In the 16^{th} century the French mathematician and philosopher René DesCartes was one of many mathematicians working on how to integrate geometry, which western civilization had inherited from the ancient Greeks, with the algebra that had been brought to Europe from Islamic civilization in the 11*Cartesian plane* or the *Cartesian coordinate system.*

The range of values of the first variable are indicated by a horizontal axis, those of the second variable by a vertical axis, and these axes intersect at the point where both are zero, at what is called the *origin*. Most often in algebra or calculus these are labeled the \(x\)-axis and the \(y\)-axis respectively, but they are in any event labeled with the symbols of the respective variables, whatever they may be.

By convention the four quadrants into which the plane is divided by the axes are referred to as quadrants I through IV, with quadrant I being the quadrant in which the values of both variables are positive, and the other quadrants numbered anti-clockwise. It is not required that the aspect ratio between the axes be the same. Rather, since the purpose of the Cartesian plane is to allow useful visual representations of numerical relations, the axes should be marked and the origin placed in whatever way promotes this.

A point in the Cartesian plane is referred to as a *coordinate pair* or *coordinates*, with the two values separated by a comma and enclosed by parentheses or angle brackets.

The first value in the coordinate pair is called the *abscissa* and the second is called the *ordinate*.

Developing a facility with drawing graphs of functions and relations in the Cartesian plane is one of the most important stages in the learning of mathematics.