What is Cartesian coordinate system?
[[Image:Cartesian-coordinate-system.svg|thumb|right|250px|Two dimensional Cartesian coordinate system. Four points are marked: (2,3) in green, (-3,1) in red, (-1.5,-2.5) in blue and (0,0), the origin, in violet.]] In [[mathematics]] and [[geometry]], the '''Cartesian coordinate system''' is a [[coordinate system]] used to give the [[location]] of [[Point (geometry)|points]] on a [[Plane (mathematics)|plane]] by using two [[number]]s for each point. It is also called the ''rectangular coordinate system''. The numbers are usually called the <math>x</math> ''coordinate'' and the <math>y</math> ''coordinate'' or sometimes the ''abscissa'' and ''ordinate''. To find the coordinates of a point, two [[Right angle|perpendicular]] [[Line|lines]], called ''axes'' (singular: ''axis''), are drawn. The point where the axes meet is the coordinate '''origin''', written (0,0). The <math>x</math> ''coordinate'' gives the [[position]] of a point measured along the <math>x</math> axis, and the <math>y</math> ''coordinate'' gives the position along the <math>y</math> axis. The coordinate system stretch's on to infinity in both ''axes.'' Cartesian coordinates can be used in [[3D|three dimensions]] (3D), by adding a third number, the <math>z</math> ''coordinate''. In [[4D|four dimensions]] (4D), a fourth number, the <math>w</math> ''coordinate'', is added. Each coordinate represents a [[dimension]] of space. Using the Cartesian coordinate system, many shapes, like straight [[line]]s and [[parabola]]s can be described by using [[Algebraic equation|algebraic equations]]. The results of the equations can be seen by plotting (drawing) a [[Point (geometry)|point]] for each solution to the [[Equation|equations]]. For example, the <math>x</math> axis is described by the equation <math>y = 0</math>. A circle having radius <math>r</math> and centered at the origin can be described with the equation <math>x^2 + y^2 = r^2</math> (see Figure 2). The name '''Cartesian''' comes from the French [[mathematician]] and [[philosopher]] [[René Descar