Cartesian coordinate system In mathematics, the Cartesian
coordinate system is used to determine each point uniquely in a
plane through two numbers, usually called the x-coordinate and
the y-coordinate of the point. To define the coordinates, two
perpendicular directed lines (the x-axis or and the y-axis or ),
are specified, as well as the unit length, which is marked off
on the two axes (see Figure 1). Cartesian coordinate systems are
also used in space (where three coordinates are used) and in
higher dimensions. Using the Cartesian coordinate system
geometric shapes (such as curves) can be described by algebraic
equations. Such equations are satisfied by the coordinates of
the points lying on the shape. For example, the circle of radius
2 may be described by the equation x² + y² = 4 (see Figure 2).
Cartesian means relating to the French mathematician and
philosopher René Descartes (Latin: Cartesius), who, among other
things, worked to merge algebra and Euclidean geometry. This
work was influential in the de