Let particle P be described by a chain of events
$\Psi ^{\sf{P}} = \left( \sf{P}_{1}, \sf{P}_{2}, \sf{P}_{3} \; \ldots \; \sf{P}_{\it{k}} \; \ldots \; \right)$
where each event is characterized by its displacement vector
$d\bar{r} = \left( dx, dy, dz \right)$
Definition: the abscissa of event $k$ is
$\begin{align} x_{k} \equiv x_{0} + \sum_{i=1}^{k} dx_{i} \end{align}$
where $x_{0}$ is arbitrary and often set to zero. The ordinate is
$\begin{align} y_{k} \equiv y_{0} + \sum_{i=1}^{k} dy _{i} \end{align}$
And the $z$-cooordinate or applicate of event $k$ is defined as
$\begin{align} z_{k} \equiv z_{0} + \sum_{i=1}^{k} dz_{i} \end{align}$
The $z$-component of the displacement $dz$ is a simple linear function of the wavelength. So if the particle is isolated then P moves in regular steps along the polar-axis as
$z_{k} = z_{0} + k dz$
The three numbers $x$, $y$ and $z$ are called the Cartesian coordinates of event $k$ after the work of René Descartes. More exactly, they are the rectangular Cartesian coordinates in a descriptive system that is centered on P. We use them to express the position of an event as$\overline{r} = ( x, y, z )$
where $\overline{r}_{0} = ( x_{0}, y_{0}, z_{0} )$. WikiMechanics uses a finite categorical scheme of binary distinctions to describe sensation. So $N$, the number of quarks in a description, may be large but not infinite. In principle $N$ is finite and accordingly displacements may be small, negligible or nil, but not infinitesimal. Later we may assume that $N$ is large enough to make an approximation to spatial continuity, then allowing the use of calculus.
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Cartesian Coordinates |