Gender shitpost Show more
Warning: Please note that "male" and "female" are deprecated genders and will no longer be supported in the future.
For more information go to:
Settings -> Gender -> About.
Rigid Foldability is NP-Hard: https://arxiv.org/abs/1812.01160
It was previously known that folding a purported origami folding pattern to a flat state is NP-hard, because you can encode logic in the way the paper gets in the way of itself. But this paper proves that it's hard even to tell whether you can make any rigid motion at all starting from completely unfolded paper, well before self-interference kicks in. Instead, the difficulty involves getting sums of angles to come out right.
A 'sum' is a sequence of terms joined by addition.
A 'product' is a sequence of terms joined by multiplication.
Is there a general term for terms joined by a general associative operation, that mathematicians would know? Is it 'sequence'?
In Haskell this would be implemented as a fold, but what do you call the thing it acts on? 'Iterable' and 'Enumerable' are too computer-sciencey.
It's possible this question has no good answer.
274. THE MOUSE-TRAP PUZZLE. This is a modern version, with a difference, of an old puzzle of the same name. Number twenty-one cards, 1, 2, 3, etc., up to 21, and place them in a circle in the particular order shown in the illustration. These cards represent mice. You start from any card, calling that card
"one," and count, "one, two, three," etc., in a clockwise direction, and when your count agrees with the number on the card, you have made a (1/4)
I'm going to Amsterdam next week, so a quick check of the Zwarte Piet situation...
Dutch people still inexplicably happy to black up: https://www.dutchnews.nl/news/2018/12/half-of-dutch-people-prepared-to-accept-changes-to-zwarte-piets-appearance/
New blog post: Triply-Hamiltonian edge colorings
In https://mathstodon.xyz/@mjd/101098853869827835, Mark Jason Dominus (@mjd) observed that the regular dodecahedron can have its edges properly colored with three colors so that every two colors form a Hamiltonian cycle. In this post, I survey constructions for more graphs like this, and prove that no planar bipartite graph can have a coloring like this.
Mathematician, koala fan, mathstodon.xyz admin,
⅓ of https://aperiodical.com
A Mastodon instance for maths people. The kind of people who make \(\pi z^2 \times a\) jokes.
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