A circular triangle is a plane figure 
bounded by three circular arcs.
By extending the arcs into complete circles,
the points of intersection 
, 
, and 
are obtained. This gives the three circular triangles 
, 
, and 
, which are called the associated
triangles to 
(Lachlan 1893, pp. 251-252).
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The circular triangle and its associated circles have a total of eight incircles and eight circumcircles. These systems of circles have some remarkable properties, including the Hart circle, which is an analog of the nine-point circle in Feuerbach's theorem.
A closed-form set of formulas for the area of circular triangles like 
is given by Fewell (2006).
A family of circular triangles that tile the plane is given by the tricurves.
