# Circles (A_{40a}), (A_{40b}), (A_{40c}), and (A_{40d}): The Outside Powerian Pairs

### Definition

The pairs of congruent circles tangent to each other at the points of tangency of the common tangent
of (O_{1}) and (O_{2}) and to the circles with centers A and B passing through C
are Archimedean and form two Powerian pairs. [van Lamoen, 2007]

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