Cartesian coordinate system
A
Cartesian coordinate system is a coordinate system that specifies each point uniquely in a plane by a pair of numerical
coordinates, which are the signed distances from the point to two fixed perpendicular directed lines, measured in the same unit of length. Each reference line is called a
coordinate axis or just
axis of the system, and the point where they meet is its
origin, usually at ordered pair. The coordinates can also be defined as the positions of the perpendicular projections of the point onto the two axes, expressed as signed distances from the origin. One can use the same principle to specify the position of any point in three-dimensional space by three Cartesian coordinates, its signed distances to three mutually perpendicular planes. In general,
n Cartesian coordinates specify the point in an
n-dimensional Euclidean space for any dimension
n. These coordinates are equal, up to sign, to distances from the point to
n mutually perpendicular hyperplanes. Cartesian coordinate system with a circle of radius 2 centered at the origin marked in red.