The word 'parametric' is used to describe methods in math that introduce an extra, independent variable called a parameter to make them work.
For example, consider the parametric equations of a circle. The circle is defined this way using two equations.
x = r cos(t) and y = r sin(t).
The parameter is t. It is a variable that is not really part of the circle,
but any given value of is t will produce an x and y value pair that lies on the circle radius r.
The parameter is t 'drives' the equation pair to cause them to produce valid coordinate pairs.
Parametric curves are defined using two separate functions, x(t) and y(t), each representing its respective coordinate and depending on a new parameter 't'. Interactive calculus applet.
A circle can be defined as the locus of all points that satisfy an equation derived from Trigonometry. Interactive coordinate geometry applet.
An ellipse can be defined as the locus of all points that satisfy an equation derived from Trigonometry. Interactive coordinate geometry applet.
(C) 2011 Copyright Math Open Reference. All rights reserved