#宮 治

[akbrsol]

[heartfeltarcher]

they both cheat in their own ways at uno

[areioshq]

Art style/skill progression is a funny thing. You know you must be improving but it's a very different feeling when you put things in a side-by-side comparison like this… the small details haven't really changed and I think that's so cute!

[bear-pattern-hamster]

"Carri-Hapi & SL銀河✨🚂🌌"

"All this sand is crystal. A small fire is burning inside."

「この砂はみんな水晶だ。中で小さな火が燃えている。」

『The Night of the Milky Way Train: 銀河鉄道の夜』

(Kenji Miyazawa: 宮沢賢治)

[gon-iii]

冬空の彩

2008年、明治神宮外苑いちょう並木。

冬の空にイチョウの色が広がる。

[saltedcaramelpops]

osamu serving as always

[azzurro-due]

[anamon-book]

時代劇博物館　島野功緒 現代教養文庫 社会思想社 カバー装画・装幀＝宮崎祐治

[key-cat]

すべてあらゆるいきものはみんな気のいい，かあいさうなものである。 けっして憎んではならん。

All the living creatures are generous, miserable things; so, you must not hate them.

宮沢 賢治 Miyazawa Kenji　

[edithsotoart]

Murasaki´s edit collection, manga, anime, and covers.

[akbrsol]

Witch AU! When you accidently summoned twin demons...

[heartfeltarcher]

osasuna

[areioshq]

Man-ag-er Miya

[bear-pattern-hamster]

"Carri-Hapi & SL銀河✨🚂🌌"

『The Night of the Milky Way Train: 銀河鉄道の夜』

(Kenji Miyazawa: 宮沢賢治)

Downstream, the Milky Way galaxy was reflected across the entire width of the river, making it look like the sky without any water.

Giovanni couldn't help but feel that Campanella was already on the edge of that galaxy.

　下流の方は川はば一ぱい銀河が巨（おお）きく写ってまるで水のないそのままのそらのように見えました。

　ジョバンニはそのカムパネルラはもうあの銀河のはずれにしかいないというような気がしてしかたなかったのです。

[gon-iii]

北参道

2010年、明治神宮 北参道。

いつも山手線の車窓からいい銀杏並木だと思っていた明治神宮の北参道。

[merpmonde]

Sangaku Saturday #4

In the previous info post, we went over the debate on the religious aspect of sangaku, and the fact that the absence of prayers on these tablets was more puzzling to some than the mathematics. As such, the tablets are not ema prayer tablets, but donations, which usually don't feature prayers on them. Case in point, some consecrated sake and French wine seen at Meiji-jingû in 2016.

Beyond wishing for good fortune and health, such donations serve two very worldly purposes: to contribute to the life and prestige of the shrine or temple (having a famous contributor makes the shrine famous by association), and to advertise the donor in return, as their name is on display. See this large torii at Fushimi Inari Taisha paid for by TV Asahi (テレビ朝日).

With that in mind, Meijizen's cynical comment from 1673 that sangaku aim "to celebrate the mathematical genius of their authors" may not far from the truth. The authors of sangaku are looking to gain notoriety through the publicity that the shrine or temple provides. But was the bemused Meijizen the target audience?

More on that in a couple of weeks. Below the cut is the solution to last week's problem.

The solution to the first problem (below the cut in this post) is the key. Name K, L and M the intersections of the three circles with the horizontal line. Then, by using that previous result,

Indeed, as in that problem, we can construct three right triangles, ABH, ACI and BCJ and apply Pythagoras's theorem in each.

Now, it suffices to note that KL = KM + LM, so

or, dividing by 2*squareroot(pqr), we get the desired result:

Inverting and squaring this yields the formula for r:

This gives us the means to construct this figure on paper using a compass and a marked ruler. Having chosen two radii p and q and constructed the two large circles (remember that AB=p+q) and a line tangent to both, placing M and C is done after calculating the lengths IK=CM=r and IC=KM=2*sqrt(pr).