Another lemma: https://www.facebook.com/photo.php?fbid=29385759224346806&set=p.29385759224346806&type=3

 

Geometria Super Top, Henry Quispe, https://www.facebook.com/photo?fbid=1873079414058745&set=gm.2372661803504175&idorvanity=830782544358783

 

Training Geometry Olympiad, Nelson Tunala, repost of Muhammed Anwar, https://www.facebook.com/photo?fbid=28235655256076250&set=gm.1737059440887695&idorvanity=293155508611436

 Use 'double angle lemma', which you may find on this blog.

Lemma by Selçuk Biçer https://www.facebook.com/photo.php?fbid=29252205531035510&set=p.29252205531035510&type=3

 

Lemma by Selçuk Biçer, https://www.facebook.com/photo.php?fbid=29286221834300546&set=p.29286221834300546&type=3

 

Trazo Geometrico Maldito, Nelson Tunala, ILL list problem, https://www.facebook.com/photo?fbid=28163237369984706&set=gm.2500067100505366&idorvanity=715291165649644

 

Training Geometry Olympiad, Aiioo Soo, https://www.facebook.com/photo/?fbid=122247242240137625&set=gm.2366635987440090&idorvanity=830782544358783