IMO Shortlist 2013 problem G1
Kvaliteta:
Avg: 3,0Težina:
Avg: 6,0 Let be an acute-angled triangle with orthocenter , and let be a point on side . Denote by and the feet of the altitudes from and , respectively. Denote by the circumcircle of , and let be the point on which is diametrically opposite to . Analogously, denote by the circumcircle of , and let be the point on which is diametrically opposite to . Prove that , and are collinear.
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