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11 votes
2 answers
455 views

Dodecahedral rolling distance

Let a dodecahedron sit on the plane, with one face's vertices on an origin-centered unit circle. Fix the orientation so that the edge whose indices are $(1,2)$ is horizontal. For any $p \in \mathbb{R}...
Joseph O'Rourke'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
14 votes
1 answer
295 views

The space of triangles that fit inside a given triangle, parametrized by edge lengths

Given a triangle T with sides a, b, and c, describe its "fitting set," the set of all points (x,y,z) in 3-dimensions for which a triangle with sides x, y, z exists that fits in T. Such a set lies in ...
John E. Wetzel's user avatar
34 votes
4 answers
2k views

About the ratio of the areas of a convex pentagon and the inner pentagon made by the five diagonals

Question : Letting $S{^\prime}$ be the area of the inner pentagon made by the five diagonals of a convex pentagon whose area is $S$, then find the max of $\frac{S^\prime}{S}$.     ...
mathlove's user avatar
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