# Circles (A_{61a}) and (A_{61b}): Dao pair

### Definition

Let E and F be the midpoints of (O_{1}) and (O_{2}) respectively.
Then let A_{61a} be the point of intersection of BE and (O_{1}), and A_{61b} the point of intersection of AF and (O_{2}).
Let G of be the point of intersection of O_{1}F and O_{2}E. The circles centered at A_{61a} and A_{61b} passing through G are Archimedean.
[Dao Thanh Oai, june 2014]

Source: A. Bogomolny, Dao's Archimedean Twins from Interactive Mathematics Miscellany and Puzzles
http://www.cut-the-knot.org/m/Geometry/DaosTwins.shtml

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