# Circle (A_{4}): Reflection of Bankoff's Quadruplet circle

### Definition

The perpendicular to OD through C meets OD in a point. The smallest circle (A_{4}) through this point tangent to the common tangent of (O_{1}) and (O_{2}) is Archimedean. [Dodge et al. 1999]

### Properties

- (A
_{4}) is the reflection of Bankoff's Quadruplet circle through the common tangent of (O_{1}) and (O_{2}). [Dodge et al. 1999]

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