  Consider two circles, externally tangential,and with integer radii R1, R2;
and with R1>R2.The two circles have three tangent lines in common, one of them
being T1T2. If M is the midpoint of T1T2, and K the point of intersection of
the lines C1C2 and T1T2;then 16 right triangles are formed(C1 and C2 are the
two circle centers), see Figure 1.In Section 6 of this paper, we find the
precice form the two integers R1 and R2 must have, in order that the sixteen
aforementioned right triangles be Pythagorean.
