Fie \( ABCD \) un patrulater convex cu \( \angle{BCD}=120\textdegree, \angle{CBA}=45\textdegree, \angle{CBD}=15\textdegree \) si \( \angle{CAB}=90\textdegree \). Sa se arate ca \( AB=AD \).
Anghel Costel
JBTST I 2010, Problema 2
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Andi Brojbeanu
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JBTST I 2010, Problema 2
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Andi Brojbeanu
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\( AB=AC \) si \( \angle BAC=2 \angle BDC \) implica faptul ca \( A \) este centrul cercului circumscris triunghiului \( BDC \).
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