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Hanoi Open Mathematics Competition 2009 Senior Question 9

HOMC · Hanoi Open Mathematics Competition 2009 Senior

Question 9

Given an acute-angled triangle $ABC$ with area $S$, define $A^{\prime}$ as the intersection of the altitude line from $A$ to $BC$ with the outward-facing semicircle on diameter $BC$. Define $B^{\prime},C^{\prime}$ cyclically. Evaluate $T=[BCA^{\prime}]^2+[CAB^{\prime}]^2+[ABC^{\prime}]^2$, where brackets denote triangle area.