P84 · Packing and covering · Classic · Hard

Equilateral triangles in a disc · n = 36

Pack n unit-side equilateral triangles into a disc. Contact is allowed; interiors cannot overlap. Minimise the container circle radius.

Instancen = 36
ObjectiveMinimize container circle radius

Record comparison

container circle radius · Lower is better
RecordValue / intervalAuthor / holderSource
External best known[2.43969, 2.4397)Thomas SchadtErich Friedman ↗
Site recordNo player record yet——

Formal definition

  • ContainerThe editor and certificate normalise the container to the closed unit disc centred at (1,1), while public scores are reported in the literature's unit-piece scale. Boundary contact is allowed.
  • SubmissionSubmit {radius, placements:[{x,y,turn},…]}, with each value written as a decimal string of at most nine places. Here x, y are centre coordinates; circles require turn = 0 and polygons use turn = tan(θ/2). Coordinates and turn must lie in [−4, 4], with 0 < radius ≤ 4.
  • ConstraintsExactly n congruent pieces lie wholly inside the container with pairwise disjoint interiors. Polygons may rotate independently by arbitrary angles.
  • PrecisionInput decimals are parsed as exact rationals and regular-polygon vertices are defined algebraically, with zero floating-point tolerance in feasibility checks.
  • ObjectiveContainer circle radius = 1/(2 sin(π/3) r), where smaller is better. Pages, leaderboards, and literature records share this unit with automatic conversion.
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Layout shown: starter layout

VERIFIED CONSTRUCTIONVERIFIED CONSTRUCTION

Getting a feel for it

Literature targets and coordinate certificates

Literature targets are converted at their published precision, while nine-decimal coordinate certificates are stored and displayed alongside the source values.

Source
The current arrangement for Equilateral triangles in a disc n = 36
LAYOUT & HISTORY

Starter layout

Inspect the layout, solver notes and record history.

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ANSWER FORMAT

How to write your answer

the closed unit disc centred at (1,1)

Submit {radius, placements:[{x,y,turn},…]}, with each value written as a decimal string of at most nine places. Here x, y are centre coordinates; circles require turn = 0 and polygons use turn = tan(θ/2). Coordinates and turn must lie in [−4, 4], with 0 < radius ≤ 4.

Starter answer

{
  "placements": [
    {
      "turn": "0.119843188",
      "x": "1.260454368",
      "y": "1.815577958"
    },
    {
      "turn": "0.119843188",
      "x": "0.839511951",
      "y": "1.774913997"
    },
    {
      "turn": "-0.427900037",
      "x": "0.609564381",
      "y": "1.718995575"
    },
    {
      "turn": "-0.427900037",
      "x": "1.056082732",
      "y": "1.654486257"
    },
    {
      "turn": "-0.427900037",
      "x": "1.423854926",
      "y": "1.644396732"
    },
    {
      "turn": "0.119843188",
      "x": "0.535804239",
      "y": "1.494009591"
    },
    {
      "turn": "-0.237398095",
      "x": "1.719247112",
      "y": "1.472288459"
    },
    {
      "turn": "-0.427900037",
      "x": "0.305856670",
      "y": "1.438091169"
    },
    {
      "turn": "0.119843188",
      "x": "0.989535721",
      "y": "1.427386609"
    },
    {
      "turn": "0.119843188",
      "x": "1.357307915",
      "y": "1.417297084"
    },
    {
      "turn": "-0.427900037",
      "x": "0.759588151",
      "y": "1.371468187"
    },
    {
      "turn": "-0.427900037",
      "x": "1.152936279",
      "y": "1.256205383"
    },
    {
      "turn": "0.119843188",
      "x": "0.239309659",
      "y": "1.210991521"
    },
    {
      "turn": "0.134412340",
      "x": "1.742157271",
      "y": "1.178986598"
    },
    {
      "turn": "0.119843188",
      "x": "0.676404601",
      "y": "1.137487116"
    },
    {
      "turn": "-0.411039993",
      "x": "1.513907437",
      "y": "1.116498456"
    },
    {
      "turn": "-0.427900037",
      "x": "0.446457031",
      "y": "1.081568694"
    },
    {
      "turn": "0.119843188",
      "x": "1.066674459",
      "y": "1.034882766"
    },
    {
      "turn": "-0.427900037",
      "x": "0.839805160",
      "y": "0.966305890"
    },
    {
      "turn": "-0.411039993",
      "x": "1.794262577",
      "y": "0.895157930"
    },
    {
      "turn": "0.134412340",
      "x": "1.453898838",
      "y": "0.887584230"
    },
    {
      "turn": "0.119843188",
      "x": "0.163990476",
      "y": "0.863162424"
    },
    {
      "turn": "-0.411039993",
      "x": "1.219935209",
      "y": "0.845966813"
    },
    {
      "turn": "0.119843188",
      "x": "0.601085418",
      "y": "0.789658018"
    },
    {
      "turn": "-0.427900037",
      "x": "0.371137849",
      "y": "0.733739596"
    },
    {
      "turn": "0.134412340",
      "x": "1.734253978",
      "y": "0.666243705"
    },
    {
      "turn": "0.119843188",
      "x": "0.998366812",
      "y": "0.658220851"
    },
    {
      "turn": "-0.427900037",
      "x": "0.764485977",
      "y": "0.618476792"
    },
    {
      "turn": "-0.411039993",
      "x": "1.506004144",
      "y": "0.603755563"
    },
    {
      "turn": "-0.427900037",
      "x": "1.167774162",
      "y": "0.492773391"
    },
    {
      "turn": "0.119843188",
      "x": "0.404964190",
      "y": "0.477227545"
    },
    {
      "turn": "0.134412340",
      "x": "1.538214718",
      "y": "0.350666591"
    },
    {
      "turn": "0.119843188",
      "x": "0.802245584",
      "y": "0.345790377"
    },
    {
      "turn": "-0.427900037",
      "x": "0.568364748",
      "y": "0.306046319"
    },
    {
      "turn": "0.119843188",
      "x": "1.201600503",
      "y": "0.236261339"
    },
    {
      "turn": "-0.427900037",
      "x": "0.971652934",
      "y": "0.180342917"
    }
  ],
  "radius": "0.236649010"
}
Submission format and technical detailsOpen this when you are ready to prepare a JSON answer+

Instance parameters

{
  "n": 36,
  "sides": 5
}

Starter answer

{
  "placements": [
    {
      "turn": "0.119843188",
      "x": "1.260454368",
      "y": "1.815577958"
    },
    {
      "turn": "0.119843188",
      "x": "0.839511951",
      "y": "1.774913997"
    },
    {
      "turn": "-0.427900037",
      "x": "0.609564381",
      "y": "1.718995575"
    },
    {
      "turn": "-0.427900037",
      "x": "1.056082732",
      "y": "1.654486257"
    },
    {
      "turn": "-0.427900037",
      "x": "1.423854926",
      "y": "1.644396732"
    },
    {
      "turn": "0.119843188",
      "x": "0.535804239",
      "y": "1.494009591"
    },
    {
      "turn": "-0.237398095",
      "x": "1.719247112",
      "y": "1.472288459"
    },
    {
      "turn": "-0.427900037",
      "x": "0.305856670",
      "y": "1.438091169"
    },
    {
      "turn": "0.119843188",
      "x": "0.989535721",
      "y": "1.427386609"
    },
    {
      "turn": "0.119843188",
      "x": "1.357307915",
      "y": "1.417297084"
    },
    {
      "turn": "-0.427900037",
      "x": "0.759588151",
      "y": "1.371468187"
    },
    {
      "turn": "-0.427900037",
      "x": "1.152936279",
      "y": "1.256205383"
    },
    {
      "turn": "0.119843188",
      "x": "0.239309659",
      "y": "1.210991521"
    },
    {
      "turn": "0.134412340",
      "x": "1.742157271",
      "y": "1.178986598"
    },
    {
      "turn": "0.119843188",
      "x": "0.676404601",
      "y": "1.137487116"
    },
    {
      "turn": "-0.411039993",
      "x": "1.513907437",
      "y": "1.116498456"
    },
    {
      "turn": "-0.427900037",
      "x": "0.446457031",
      "y": "1.081568694"
    },
    {
      "turn": "0.119843188",
      "x": "1.066674459",
      "y": "1.034882766"
    },
    {
      "turn": "-0.427900037",
      "x": "0.839805160",
      "y": "0.966305890"
    },
    {
      "turn": "-0.411039993",
      "x": "1.794262577",
      "y": "0.895157930"
    },
    {
      "turn": "0.134412340",
      "x": "1.453898838",
      "y": "0.887584230"
    },
    {
      "turn": "0.119843188",
      "x": "0.163990476",
      "y": "0.863162424"
    },
    {
      "turn": "-0.411039993",
      "x": "1.219935209",
      "y": "0.845966813"
    },
    {
      "turn": "0.119843188",
      "x": "0.601085418",
      "y": "0.789658018"
    },
    {
      "turn": "-0.427900037",
      "x": "0.371137849",
      "y": "0.733739596"
    },
    {
      "turn": "0.134412340",
      "x": "1.734253978",
      "y": "0.666243705"
    },
    {
      "turn": "0.119843188",
      "x": "0.998366812",
      "y": "0.658220851"
    },
    {
      "turn": "-0.427900037",
      "x": "0.764485977",
      "y": "0.618476792"
    },
    {
      "turn": "-0.411039993",
      "x": "1.506004144",
      "y": "0.603755563"
    },
    {
      "turn": "-0.427900037",
      "x": "1.167774162",
      "y": "0.492773391"
    },
    {
      "turn": "0.119843188",
      "x": "0.404964190",
      "y": "0.477227545"
    },
    {
      "turn": "0.134412340",
      "x": "1.538214718",
      "y": "0.350666591"
    },
    {
      "turn": "0.119843188",
      "x": "0.802245584",
      "y": "0.345790377"
    },
    {
      "turn": "-0.427900037",
      "x": "0.568364748",
      "y": "0.306046319"
    },
    {
      "turn": "0.119843188",
      "x": "1.201600503",
      "y": "0.236261339"
    },
    {
      "turn": "-0.427900037",
      "x": "0.971652934",
      "y": "0.180342917"
    }
  ],
  "radius": "0.236649010"
}

Submit {radius, placements:[{x,y,turn},…]}, with each value written as a decimal string of at most nine places. Here x, y are centre coordinates; circles require turn = 0 and polygons use turn = tan(θ/2). Coordinates and turn must lie in [−4, 4], with 0 < radius ≤ 4. · Verifier v1.0.0

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