Generalized problem of Geometria Top, Hajj Mustafa El-Rardini, https://www.facebook.com/photo/?fbid=6710749308942650&set=gm.1087931558643879

A piece of my book, 'Rose thorns - Geometry jewels', I called it 'Triple angle lemma'. The proof is mine.

 

Nelson Tunala, Geometria Top, https://www.facebook.com/photo/?fbid=3907884295946685&set=gm.962288931208143

 

Nelson Tunala, Geometria Top, https://www.facebook.com/photo/?fbid=3914651885269926&set=gm.963789431058093

 

Stanford Li, Training Geometry Olympiad, https://www.facebook.com/photo?fbid=10224737947489560&set=gm.582578046335846

 A synthetic solution:

Mongolian SL 2000 Math Olympiad, https://www.facebook.com/photo?fbid=4456586367743139&set=gm.1744931542378025

 

aophttps://artofproblemsolving.com/community/c6t48f6h2483365_amxcp__bnxdq_is_constant_projections_of_square_on_tangents,

 

Abdilkadir Altintas, Geometria Top, https://www.facebook.com/photo?fbid=3025600111102321&set=gm.1076995453070823