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35 votes
5 answers
3k views

Tiling the plane with incongruent isosceles triangles

It is not difficult to tile the plane with incongruent triangles. One could tile with equilateral triangles, and then partition each equilateral into three triangles, displacing their common ...
Joseph O'Rourke's user avatar
12 votes
1 answer
373 views

A claim on partitioning a convex planar region into congruent pieces

Let us define a perfect congruent partition of a planar region $R$ as a partition of it with no portion left over into some finite number n of pieces that are all mutually congruent (ie any piece can ...
Nandakumar R's user avatar
  • 5,979
17 votes
1 answer
458 views

The sparsest planar net that captures every unit segment

Let $\cal C = \lbrace C_i \rbrace$ be a collection of rectifiable curves in the plane with the property that every unit-length segment meets at least one curve in at least one point. Call such a ...
Joseph O'Rourke's user avatar
11 votes
1 answer
499 views

Tiling with incommensurate triangles

Say that two triangles are incommensurate if they do not share an edge length or a vertex angle, and their areas differ. Suppose you'd like to tile the plane with pairwise incommensurate triangles. I ...
Joseph O'Rourke's user avatar
6 votes
0 answers
176 views

Optimal planar net for catching convex shapes

Imagine you want to make a net out of string to filter and catch objects of a certain size, minimizing the length of string employed. (This actually arises in filtering biological impurities from ...
Joseph O'Rourke's user avatar
22 votes
1 answer
1k views

Aperiodic monotile without reflections?

The recently discovered amazing aperiodic monotile (or "einstein") of David Smith, Joseph Samuel Myers, Craig S. Kaplan, and Chaim Goodman-Strauss tiles the plane only if reflections of the ...
Timothy Chow's user avatar
  • 82.7k
14 votes
5 answers
2k views

How can one construct a four-coloring of a tiling of the plane with Smith, Myers, Kaplan, and Goodman-Strauss's aperiodic monotile?

This is motivated by the new paper of Smith, Myers, Kaplan, and Goodman-Strauss, wherein they define the existence of an aperiodic monotile. Clearly their tiling is not three-colorable, so we have ...
Lucas Blakeslee's user avatar
9 votes
1 answer
282 views

Thinnest covering of the plane by regular pentagons

Q. Is it known what is the thinnest covering of the infinite plane by regular pentagons? By covering I mean every point of the plane is covered. By thinnest I mean the proportion of the plane covered ...
Joseph O'Rourke's user avatar
3 votes
1 answer
152 views

Triangles that can be cut into mutually congruent and non-convex polygons

It is easy to note that an equilateral triangle can be cut into 3 mutually congruent and non-convex polygons (replace the 3 lines meeting at centroid and separating out the 3 congruent quadrilaterals ...
Nandakumar R's user avatar
  • 5,979
2 votes
1 answer
235 views

Tiling with one of each shape

Q. Is there a tiling of the plane by one each of simple polygons of $n$ vertices: one triangle, one quadrilateral, one pentagon, $\ldots$ , one simple polygon of $n$ vertices, $\ldots$ ? Here a ...
Joseph O'Rourke's user avatar