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Pick’s Theorem Asher Auel Department of Mathematics Yale University Pathways to Science Café October 5th, 2014

Pick’s Theorem - Mathematics at Dartmouthauel/papers/docs/sciencecafe.pdf · Pick’s Theorem Asher Auel ... Area = 3 = 3 2 2? 11 2 1 3 Area = 9 51 2 = 3 1 2. Georg Alexander Pick

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  • Pick’s Theorem

    Asher Auel

    Department of MathematicsYale University

    Pathways to Science CaféOctober 5th, 2014

  • Area = 3

  • 1 1

    1 1

    12

    Area = 412

  • 1 2

    Area = 3

  • 2

    3

    Area = 3 = 3×22

  • Area = 3 = 3×22

  • Area = 3 = 3×22

  • ?

  • 1 12

    1 3

    Area = 9 − 512 = 312

  • Georg Alexander Pick 1859–1942

  • A lattice polygon has all of its vertices on lattice points.

    i = the number of lattice points strictly inside

    b = the number of lattice points on the perimeter

    Pick’s TheoremThe area of a lattice polygon is

    A = i +b2− 1

  • A = i + b2 − 1 3 +32 − 1 = 3

    12

  • A = i + b2 − 1 0 +82 − 1 = 3

  • A = i + b2 − 1 2 +72 − 1 = 4

    12

  • A = i + b2 − 1 0 +32 − 1 =

    12

  • A = i + b2 − 1 0 +32 − 1 =

    12

  • A = i + b2 − 1

    = 2 + 62 − 1

    THE

    E

    D

  • Ford circles

  • Farey sequences

    01,

    11

    01,

    12,

    11

    01,

    13,

    12,

    23,

    11

    01,

    14,

    13,

    12,

    23,

    34,

    11

    01,

    15,

    14,

    13,

    25,

    12,

    35,

    23,

    34,

    45,

    11

    01,

    16,

    15,

    14,

    13,

    25,

    12,

    35,

    23,

    34,

    45,

    56,

    11

    01,

    17,

    16,

    15,

    14,

    27,

    13,

    25,

    37,

    12,

    47,

    35,

    23,

    57,

    34,

    45,

    56,

    67,

    11