## A Scalene Triangle Determines How Many Circles?

The question: a scalene triangle determines exactly how many circles, where only the vertices of the triangle are uniquely used, or the body of the triangle in general (i.e. no arbitrarily specified points, such as the midpoint of any of the sides, are used to determine a circle)? The answer is surprisingly high! Key thoughts: a circle can be uniquely determined by 3 non-collinear points (3 points), or by a diameter (requiring 2 points), or by a center and a radius (also 2 points)[seems a little like the ID's for getting a driver's license, doesn't it?]. Sounds simple -- until you realize that geometrical constraints can be used to yield additional points to use beyond just the three vertices [come to think of it, can it just be a coincidence that your driver's test included a *3-point* turn?]. So, there are inscribed and circumscribed circles (total, 2); circles centered at each vertex and using each side as a radius (total, 6); circles... read more