Uploaded July 2025 | Updated September 2026, 2 weeks ago

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This seemingly simple geometry problem got a lot of traffic recently on r/askmath, as many tried to solve it, got it wrong, and got stuck. The OP’s wife, a math teacher, was unable to solve it - and this time that’s not because the teacher is incompetent but the problem is simply much harder than it looks. We’ll solve this variation of Langley’s Adventitious Angles using some clever geometric constructions and basic properties of triangles. #geometryproblems #mathchallenge

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SOURCES
reddit.com/r/askmath/comments/1lq21qv/my_wife_math_teacher_cannot_figure_this_out
reddit.com/r/askmath/comments/1lqy3vj/comment/n18lc4a/?context=3
mathwithbaddrawings.com/2015/06/10/trick-or-technique
Tripp, Colin. “Adventitious Angles.” The Mathematical Gazette, vol. 59, no. 408, 1975, pp. 98–106. JSTOR, doi.org/10.2307/3616644.
duckware.com/tech/worldshardesteasygeometryproblem.html
Adventitious angles problem: the lonely fractional derived angle by Yong Kong and Shaowei Zhang

MUSIC
Special World 8 (Crown) - Super Mario 3D Land
Athletic BGM (Super Mario World 2 - Yoshi's Island) - Mario Kart World
Musee Champignon
Aquatic Ambience
Torigoth - Night
Ordon Village
Dire Dire Docks
Mario 64 End Theme

0:00 Intro
1:09 Hogwash Montage
3:19 What's the Deal?
5:33 Adventitious
7:25 Solution
19:10 Conclusion