FB page of Nelson Tunala, https://www.facebook.com/photo?fbid=9805651689503220&set=gm.945940134183217&idorvanity=569006668543234

 

Thiago Durado, I love Geometry, https://www.facebook.com/photo?fbid=997024679265157&set=gm.1449671353068533&idorvanity=970715314297475

 

Geometria Super Top, Thiago Durado, https://www.facebook.com/photo?fbid=995487406085551&set=gm.1959699281467098&idorvanity=830782544358783

 

Training Geometry Olympiad, Rachid Iksi, https://www.facebook.com/photo?fbid=4196990373868099&set=gm.1351103066150003&idorvanity=293155508611436

 

Aops, https://artofproblemsolving.com/community/c6t48f6h2381913_60o_angle_wanted_equilateral_on_a_square

 

Math For Change, https://www.facebook.com/search/top?q=alpha%20beta%20math

 

Geometria Super Top, Thiago Durado, https://www.facebook.com/photo?fbid=993563456277946&set=a.304452958522336

 

FB page of Nelson Tunala, https://www.facebook.com/photo/?fbid=9759876830747373&set=a.542610499140765

 

Aops, https://artofproblemsolving.com/community/c6t48f6h3575848_problem_3

 

aops, Walther Janous, https://artofproblemsolving.com/community/c6t48f6h2352132_segment_of_projections_is_half_as_sidelength_right_triangle_inscribed_in_right

 

aops, https://artofproblemsolving.com/community/c4t48f4h3566279_incircle_concurrency

 The green marked angles are equal

FB page of Alpha Beta Math, https://www.facebook.com/photo?fbid=122134873910752641&set=a.122096449862752641

 

Nelson Tunala, Geometria Super Top, https://www.facebook.com/photo?fbid=9700785399989850&set=gm.1951914485578911&idorvanity=830782544358783

 

FB Alpha Beta Math, https://www.facebook.com/profile.php?id=61572579235822

 

Math for Change, https://www.facebook.com/profile.php?id=61572579235822

 

FB page of Nelson Tunala, https://www.facebook.com/photo/?fbid=9682593625142361&set=a.542610499140765

 This is my solution found back in Dec. 1989

Problem, Michael de Villiers, https://www.facebook.com/groups/293155508611436

 

Thiago Durado, https://www.facebook.com/photo/?fbid=984384123862546&set=gm.1436606227708379&idorvanity=970715314297475

 

Edson Curahua Ortega, https://www.facebook.com/photo?fbid=379969052114132&set=a.379968675447503

 My solution to this nice lemma, which I call "triple angle lemma".