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On This Day

  • 7-26-1941

    Henri Lebesgue died in Paris, France. He invented measure theory in 1901 and the Lebesgue integral in 1902.

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    Henri Lebesgue
  • 7-26-1942

    Georg Pick died in the Nazi concentration camp at Theresienstadt, Bohemia (now Czech Republic) at the age of 82. Pick worked in a number of mathematical fields, but is best known for Pick's Theorem giving the area of a polygon in terms of the number of lattice points in its interior and on its boundary.

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    Georg Alexander Pick
  • 7-26-1976

    Solution to the Four Color Problem. Kenneth Appel and Wolfgang Haken of the University of Illinois communicated their proof of the Four Color Theorem to the "Bulletin of the American Mathematical Society. The proof used over 1000 hours of computer calculation.

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    Four Color Theorem
    Kenneth Appel
    Wolfgang Haken