Search: +meta:BP508
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BP989 |
| Number of dots is n factorial for some n vs. not so. |
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BP991 |
| Can be arranged with multiple copies of itself to form some convex shape vs. not so. |
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BP992 |
| Concave shapes with concave cavities vs. convex cavities |
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COMMENTS
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All examples in this Problem are solid concave black shapes. In this Problem, the "cavities" of a concave shape are defined to be the convex hull of the shape minus the shape itself. For example, if you take a bite out of the edge of a piece of paper, the piece of paper in your mouth is the cavity of the bitten piece of paper. The idea may be indefinitely extended, considering whether the cavities of the cavities are concave or convex, and so on. |
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CROSSREFS
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Adjacent-numbered pages:
BP987 BP988 BP989 BP990 BP991  *  BP993 BP994 BP995 BP996 BP997
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KEYWORD
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nice, precise, perfect, traditional
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CONCEPT
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recursion_number (info | search), recursion (info | search)
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WORLD
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concave_fill_shape [smaller | same | bigger]
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AUTHOR
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Jago Collins
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BP993 |
| Net corresponds do a unique solid vs. net can be folded into multiple different solids. |
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BP994 |
| Net corresponds to a solid that can tessellate 3D space vs. net does not correspond to a solid that can tessellate 3D space. |
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COMMENTS
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More specifically these solids are polyhedra, and are often called "space-filling".
There is ambiguity here regarding some nets that can be folded to make multiple different solids. For example EX8175 could correspond to a cuboid with a pyramid-like protrusion at each end, a protrusion at one end and an indent at the other, or 2 indents. Only the second of these options can tessellate 3D space. For clarity's sake examples like this are not sorted on either side. |
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CROSSREFS
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Adjacent-numbered pages:
BP989 BP990 BP991 BP992 BP993  *  BP995 BP996 BP997 BP998 BP999
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KEYWORD
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stub, precise, 3d, perfect, preciseworld
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CONCEPT
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3d_net (info | search), 3d_solid (info | search)
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WORLD
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polyhedron_net [smaller | same | bigger]
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AUTHOR
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Leo Crabbe
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BP996 |
| Net corresponds to a convex solid vs. net corresponds to a concave solid. |
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BP997 |
| There exists a loop that passes through every white square once without passing through the black square vs. there exists no such loop. |
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BP1011 |
| Polygon can be inscribed in a circle vs. not so. |
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