Let three circles be located such that their centers are non-collinear.

Construct a fourth circle that is orthogonal to each of the three circles.

(In reply to What is geometric construction? by Dej Mar)

To answer the question in the subject line, a geometric construction traditionally is limited to use of straightedge and compass.  It's not numerical or algebraic (i.e., not Cartesian, but rather, Euclidean).

Posted by Charlie on 2008-05-26 12:56:51