Vertical line test

Revision as of 10:45, 1 July 2006 by Mathnerd314 (talk | contribs)

The vertical line test states that:

A relation is a function iff no vertical line intersects the graph in more than one point.

For example, $y=x^2$ is a function because any vertical line intersects it in at most one point, while $x^2+y^2=1$ is not a function (try x=0).