A Collinearity Involving an Excircle, the Incircle, and the Circumcircle

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Let ABC be a triangle with incenter I and circumcircle . Let J be the excenter of the excircle opposite A. Let IJ intersect BC at D and let IJ intersect at M. Let N be the midpoint of arc MBA of . Let S and T be the second intersection points of NI, NJ with . Then S, D, T are collinear.

Contributed by: Jay Warendorff (March 2011)
Open content licensed under CC BY-NC-SA



See collinear excircle.

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