Alexander James Sirens, Geometria Super Top, https://www.facebook.com/photo?fbid=3273583526155247&set=gm.2276029139834109&idorvanity=830782544358783

 

Thiago Durado, I Love Geometry, https://www.facebook.com/photo?fbid=1283481923952763&set=gm.1722055809231726&idorvanity=1216680106435968

 

Thiago Durado, Geometria Super Top https://www.facebook.com/photo?fbid=1282033827430906&set=gm.2271128366990853&idorvanity=830782544358783

 

Thiago Durado, I Love Geometry https://www.facebook.com/photo?fbid=26908591615449294&set=gm.972472982159415&idorvanity=195960136477374

 

Selçuk Biçer, Geometria Super Top https://www.facebook.com/photo/?fbid=27989747883947954&set=gm.2272984176805272&idorvanity=830782544358783

 

Selçuk Biçer, Geometria Super Top https://www.facebook.com/photo?fbid=27986904327565643&set=gm.2272807920156231&idorvanity=830782544358783

 

Trazos Auxiliares en Geometria, Nelson Tunala, https://www.facebook.com/photo?fbid=26869205252721264&set=gm.970115739061806&idorvanity=195960136477374

 

Geometria Super Top, Fatih Eymen Hallaç, https://www.facebook.com/photo?fbid=10163777728503190&set=gm.2270719707031719&idorvanity=830782544358783

 For explanation and proof of triple angle lemma you may scroll my blog!

aops, https://artofproblemsolving.com/community/c4t48f4h2035282_dab90oadc___bam____adb___cam_kharkiv_city_x_2017_ukr

 

Nelson Tunala, Trazos Auxiliares en Geometria, https://www.facebook.com/photo?fbid=26831171749857948&set=gm.967353269338053&idorvanity=195960136477374

 

Alexander James Sirens, Geometria Super Top, https://www.facebook.com/photo?fbid=3264273037086296&set=gm.2267871483983208&idorvanity=830782544358783

 

John Tsilai, Math Lovers, https://www.facebook.com/photo?fbid=3195025937372122&set=gm.2221539305261075&idorvanity=319322575482767

 

Geometria Super Top, Alexander James Sirens, https://www.facebook.com/photo?fbid=3259799400866993&set=gm.2264051727698517&idorvanity=830782544358783

 

Nelson Tunala, Pre Geometria Trigonometria https://www.facebook.com/photo?fbid=26334807416161053&set=gm.4310259995883206&idorvanity=1660116210897611

 

Mi Prepa, https://www.facebook.com/photo?fbid=1427344626075511&set=a.575642501245732

 

Mi Prepa, https://www.facebook.com/photo?fbid=1427344626075511&set=a.575642501245732

In the interior of triangle ABC having  there is a point D having . Find .

Proof:

Take E reflection of B across CD, it lies onto CA and D is the circumcenter of ; according to lemma proved at https://stanfulger.blogspot.com/2026/05/problem-lost-source.html,
AE = AD. With  we infer .

Problem, lost source

 

Geometria Super Top, Alexander James Sirens, https://www.facebook.com/photo?fbid=3252905348223065&set=gm.2258144711622552&idorvanity=830782544358783

 

Geometria Super Top, Selcuk Bicer, https://www.facebook.com/photo?fbid=27762870359969042&set=gm.2257061028397587&idorvanity=830782544358783

 

Geometria Super Top, Mathci Jafar, https://www.facebook.com/photo?fbid=122106150452693674&set=gm.2253371212099902&idorvanity=830782544358783

 

Gogeometry, Antonio Gutierrez, https://gogeometry.blogspot.com/2023/03/geometry-problem-1523-discover-how-to.html

 

Aops, Erik Lim, https://artofproblemsolving.com/community/c6t48f6h3821925_angle_aob_in_a_triangle_with_a_bisector_and_ratio_point

 

Fatih Eymen Hallac, https://www.facebook.com/photo?fbid=10163652155783190&set=gm.964231823089984&idorvanity=418649204314918

 

Romantics of Geometry, Nelson Tunala, repost of Confident Bee3824, in 'Trazos Auxiliares en Geometria', https://www.facebook.com/photo/?fbid=26405872469054547&set=gm.26727441590276194&idorvanity=1019808738132832

 

Gogeometry, Antonio Gutierrez, problem 920,

Gogeometry, Antonio Gutierez, https://gogeometry.com/school-college/6/p1582-outside-point-secants-circle-equal-angles-cyclic-quadrilateral-problem.html

 

Gogeometry, AntonioGutierez, https://gogeometry.com/school-college/6/p1591-quadrilateral-ABCD-congruent-sides-proportional-angles-7-10-5-calculate-angle-D.html

 

Gogeometry, Antonio Gutierez, https://www.gogeometry.com/school-college/4/p1389-triangle-40-20-degree-angle-congruence-tutoring.htm

 

Gogeometry, Antonio Gutierez, https://gogeometry.com/school-college/6/p1565-triangle-median-perpendicular-midpoint-congruence-tutoring.html

 

Geometria Super Top, WayMoorthy Moorthy, https://www.facebook.com/photo?fbid=957222900020724&set=gm.2234370147333342&idorvanity=830782544358783

 

Geometria Super Top, https://www.facebook.com/photo/?fbid=3223494744497459&set=gm.2232901260813564&idorvanity=830782544358783

 

AOPS https://artofproblemsolving.com/community/c4t48f4h3801861_mtrp_2024_junior_online_integer_3

 

Anie Luc, posted by Chris Wildhagen, https://www.facebook.com/photo?fbid=1568765494283961&set=gm.2085688605534831&idorvanity=830782544358783

 

Comunitatea Profesorilor de Matematica din Romania, Turkiye Contest, https://www.facebook.com/photo?fbid=122190801800433379&set=gm.4458278801126780&idorvanity=1467372433550780

 

Geometria Super Top, Miguel Angel Tintaya, https://www.facebook.com/photo?fbid=122182183466785001&set=gm.2225670991536591&idorvanity=830782544358783

 

I Love Geometry, WayMoorthy Moorthy, https://www.facebook.com/photo/?fbid=947191211023893&set=gm.1675276253909682&idorvanity=1216680106435968

 

Les Perles Mathematiques, Naibe Pereira, https://www.facebook.com/photo?fbid=122171191358801239&set=gm.2707879176278627&idorvanity=183174185415818

 

Les Perles Mathematiques, Zekai Can, https://www.facebook.com/photo?fbid=27110413065228090&set=gm.2705192539880624&idorvanity=183174185415818

 

Geometria Super Top, Anie Luc, https://www.facebook.com/photo?fbid=122151159656416607&set=gm.2190231108413913&idorvanity=830782544358783

 

Nelson Tunala, Training Geometry Olympiad, https://www.facebook.com/photo?fbid=26162586553383141&set=gm.1594923915101249&idorvanity=293155508611436

 

Training Geometry Olympiad, David Vreken, https://www.facebook.com/photo?fbid=10166811342893356&set=gm.1591675655426075&idorvanity=293155508611436

 

Dorinel Anca, https://www.facebook.com/photo?fbid=122189173670433379&set=gm.4441467006141293&idorvanity=1467372433550780

 

George Tsikaloudakis, I Love Geometry, https://www.facebook.com/photo?fbid=2371405353357808&set=gm.1665589368211704&idorvanity=1216680106435968

 

Geometria Super Top, Miguel Angel Tintaya, https://www.facebook.com/photo?fbid=122180431154785001&set=gm.2212589872844703&idorvanity=830782544358783

 

Training Geometry Olympiad, https://www.facebook.com/photo?fbid=2069777933960574&set=gm.1195342872678580&idorvanity=410331654513043

 

Erdem Balkan, Geometria Super Top, https://www.facebook.com/photo?fbid=25887346077632954&set=gm.2200828027354221&idorvanity=830782544358783

 

Comunitatea Profesorilor de Matematica din Romania, Dorinel Anca, https://www.facebook.com/photo?fbid=122188313486433379&set=gm.4432210257066968&idorvanity=1467372433550780

 

Geometria Super Top, Anonymous Participant, https://www.facebook.com/photo/?fbid=3258267951025277&set=gm.2206643150106042&idorvanity=830782544358783

 

Geometria Super Top, Fatyh Eymen Hallaç, https://www.facebook.com/photo?fbid=10163429481193190&set=gm.2202568100513547&idorvanity=830782544358783

 

Geometria Super Top, Anie Luc, https://www.facebook.com/photo?fbid=122151056636416607&set=gm.2188242201946137&idorvanity=830782544358783

 A soution using both synthetic & metric solution:

Fly Can, https://www.facebook.com/photo?fbid=946922227869134&set=gm.1573448447080342&idorvanity=544207276671136

 

Geometria Super Top, https://www.facebook.com/photo?fbid=1455912716165133&set=gm.2199590264144664&idorvanity=830782544358783