The center of dilation has a coordinate of and the scale factor is . The <em>transformation</em> formula is .
<h3>How to define a dilation between two concentric circles</h3>
Two circles are <em>concentric</em> when they share the same center () but they have different radii (), where corresponds to the radius of the <em>smaller</em> circle. By analytic geometry we know that circles are modeled after this formula:
(1)
If we assume that the center of dilation is the center of both circles and the dilation use a scale factor of . Then, we have the following expression:
(2)
The center of dilation has a coordinate of and the scale factor is . The <em>transformation</em> formula is .