Mark:
CIRCLES
As I suspected, the answer is zero. The three points are collinear.
Using a formula I found that gives the equation of the line formed by the two intersection points, I was able to determine that it bisectes AA'.

'
The three vertices of the ``triangle'' are always on the radical axis of C and C'!
Similarly, if C and C' are disjoint, there are four line segments tangent to both circles at their endpoints; the resulting four midpoints are collinear, the common line being again the radical axis.
Likewise in higher dimensions. For instance, three spheres close enough to intersect usually meet in two points, call them again P and Q, and have two planes tangent to all three spheres. For each of the planes, assume that the three points of tangency are not collinear, and consider the center of the unique circle through all three. Then P, Q, and the two circumcenters lie on the radical axis of the three spheres, and are thus collinear. If the spheres are disjoint, there can be as many as eight planes tangent to all three; this yields eight circumcenters, all on the radical axis and thus collinear.
What pie quiz?
Pi is transcendental. What does it mean for a number to be transcendental
A. It is equal to the ratio of two integers.
B. It cannot be expressed as the solution of any polynomial with integer coefficients.
C. It is Ralph Waldo Emerson's favorite number.
D. Its square root is equal to -1.
E. Its decimal expansion is infinite in length.
If you pick any two integers at random, what is that probability that they will be relatively prime
("relatively prime" means that the two numbers share no divisors except 1)
A. pi/2
B. pi/3
C. 1/pi
D. 6/(pi^2)
E. pi^2/9