Weill's theorem states that, given the incircle and circumcircle of a bicentric
polygon of
sides, the centroid of the tangent points on the incircle
is a fixed point ,
known as the Weill point, independent of the particular
polygon.
More generally, the locus of the centroid of any number of the
points is a circle (Casey 1888).
sides, the centroid of the tangent points on the incircle
is a fixed point 
,
known as the Weill point, independent of the particular
polygon.
points is a circle (Casey 1888).
