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アローラのポンスレ定理🍣┗(↑o↑)┛＜ｴｩﾝｪｩｩｩｩｩﾝ壁打ちはこのポジティブフィードバックがあるからやめられねえ、偶然見た貧相な日本語の記事 <a href="https://fla.red/tags/jawp" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#JAWP</a> 「双心四角形」 <a href="https://ja.wikipedia.org/wiki/%E5%8F%8C%E5%BF%83%E5%9B%9B%E8%A7%92%E5%BD%A2" rel="nofollow noopener noreferrer" target="_blank">https://ja.wikipedia.org/wiki/%E5%8F%8C%E5%BF%83%E5%9B%9B%E8%A7%92%E5%BD%A2</a> 文章少ないとはいえ大事な部分がスグ分かってイイ！さらに <a href="https://fla.red/tags/enwp" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#ENWP</a> 「Cyclic quadrilateral」 <a href="https://en.wikipedia.org/wiki/Cyclic_quadrilateral" rel="nofollow noopener noreferrer" target="_blank">https://en.wikipedia.org/wiki/Cyclic_quadrilateral</a> も見たら、四辺決まれば面積も外接円も二対角線も決まる形というややこしさ。ってかコレも三辺長固定で動かして最小半径になるのが双心四角形だったりするのか（最大は無限であることは自明）いや最小は丁度三角形になるときだろうし、ってか三角不等式的な辺の制約からやって、基本的には$a,c',b,a',c,b'$の六辺形をベースに考えるとか、むしろ本筋は四辺の和（周長）を一定な数 <a href="https://hayabusa.open2ch.net/test/read.cgi/news4vip/1475904354/" rel="nofollow noopener noreferrer" target="_blank">https://hayabusa.open2ch.net/test/read.cgi/news4vip/1475904354/</a> として三辺の比から最大最小外接円とかが面白いかも、まあやらんけど終

㈰㈪㈫㈬㈭金正月About "One Generalization of Langley’s Adventitious Angles" <a href="https://twitter.com/wasanp_/status/1112551634729463809" target="_blank" rel="nofollow noopener noreferrer" translate="no">https://twitter.com/wasanp_/status/1112551634729463809</a> ( <a href="https://mathstodon.xyz/tags/ENWP" class="mention hashtag" rel="tag">#ENWP</a> "Langley’s Adventitious Angles <a href="https://mathstodon.xyz/tags/Generalization" class="mention hashtag" rel="tag">#Generalization</a> " <a href="https://en.wikipedia.org/wiki/Langley’s_Adventitious_Angles#Generalization" target="_blank" rel="nofollow noopener noreferrer" translate="no">https://en.wikipedia.org/wiki/Langley’s_Adventitious_Angles#Generalization</a> ) like a image, I do not know Euclid's elementary geometrical proof (?=30[°]). Thanks!（Twitterでもインチキ英語他いろいろ間違ってたので、まあ添付図の問題が解ければ同様に解けそうだけど、俺は諦めたので）全く関係ないけど、土曜日に解かなきゃいけないと自分に課した問題として、ある人物が頑張っているという整数$ 0 \le p \le q $の上で $\sin\theta=\sqrt{\frac{p}{q}}$となるθの規則性を知りたい的なピタゴラス整辺問題の純粋な拡張をどげんかせんと遷都せんといかん（続

㈰㈪㈫㈬㈭金正月<a href="https://mathstodon.xyz/@jsiehler" class="u-url mention">@jsiehler</a> Your discovery is very beautiful, and I find the answer "a=55, b=44, c=29". First, I remembered <a href="https://mathstodon.xyz/tags/ENWP" class="mention hashtag" rel="tag">#ENWP</a> "Volume of a tetrahedron (Tartaglia's formula)=0" <a href="https://en.wikipedia.org/wiki/Niccol%C3%B2_Fontana_Tartaglia#Volume_of_a_tetrahedron" target="_blank" rel="nofollow noopener noreferrer" translate="no">https://en.wikipedia.org/wiki/Niccol%C3%B2_Fontana_Tartaglia#Volume_of_a_tetrahedron</a> . Next, I tried to solve the equation b=36+x, c=26+y (x=1,2,…,9, y=1,2,…9) with <a href="https://mathstodon.xyz/tags/WolframAlpha" class="mention hashtag" rel="tag">#WolframAlpha</a> <a href="https://www.wolframalpha.com/input/?i=det(%7B%7B0,10%5E2,26%5E2,36%5E2,1%7D,%7B10%5E2,0,(26%2B3)%5E2,(36%2B8)%5E2,1%7D,%7B26%5E2,(26%2B3)%5E2,0,a%5E2,1%7D,%7B36%5E2,(36%2B8)%5E2,a%5E2,0,1%7D,%7B1,1,1,1,0%7D%7D)%3D0" target="_blank" rel="nofollow noopener noreferrer" translate="no">https://www.wolframalpha.com/input/?i=det(%7B%7B0,10%5E2,26%5E2,36%5E2,1%7D,%7B10%5E2,0,(26%2B3)%5E2,(36%2B8)%5E2,1%7D,%7B26%5E2,(26%2B3)%5E2,0,a%5E2,1%7D,%7B36%5E2,(36%2B8)%5E2,a%5E2,0,1%7D,%7B1,1,1,1,0%7D%7D)%3D0</a> (it can't be solved automatically, so I searched manually one by one.). The general solution was unknown to me, but I was very interesting!Thanks!

㈰㈪㈫㈬㈭金正月Now I found a related article in <a href="https://mathstodon.xyz/tags/OEIS" class="mention hashtag" rel="tag">#OEIS</a> <a href="http://oeis.org/A102766" target="_blank" rel="nofollow noopener noreferrer" translate="no">http://oeis.org/A102766</a> . It's seem to relate <a href="https://mathstodon.xyz/tags/ENWP" class="mention hashtag" rel="tag">#ENWP</a> 「Kaprekar number」 <a href="https://en.wikipedia.org/wiki/Kaprekar_number" target="_blank" rel="nofollow noopener noreferrer" translate="no">https://en.wikipedia.org/wiki/Kaprekar_number</a> . It's new to me. Thanks!

㈰㈪㈫㈬㈭金正月<a href="https://mathstodon.xyz/tags/ENWP" class="mention hashtag" rel="tag">#ENWP</a> "Machin-like formula" <a href="https://en.wikipedia.org/wiki/Machin-like_formula" target="_blank" rel="nofollow noopener noreferrer" translate="no">https://en.wikipedia.org/wiki/Machin-like_formula</a> \[ 4\arctan \frac{1}{5} -\arctan \frac{1}{239} =\frac{\pi}{4} \] , I like Eular's formula $\displaystyle \frac{\pi}{4} =\arctan \frac{1}{2} +\arctan \frac{1}{3} $. I use website "Easy Copy <a href="https://mathstodon.xyz/tags/MathJax" class="mention hashtag" rel="tag">#MathJax</a> " <a href="http://easy-copy-mathjax.xxxx7.com/#trigonometric-function-etc" target="_blank" rel="nofollow noopener noreferrer" translate="no">http://easy-copy-mathjax.xxxx7.com/#trigonometric-function-etc</a>

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