Problem 364. Obtuse triangle, Congruence, Circles, Diameter,
Curvilinear triangle, Area. Level: High School, College, SAT
Prep.
The figure shows an obtuse triangle ABC (angle B obtuse) of area S. D is the circumcenter of triangle ABC. Circles of diameters AD, BD, and CD form a curvilinear triangle of area S_{1}. Prove that S = 2S_{1}.

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