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  2. Sentence (mathematical logic) - Wikipedia

    en.wikipedia.org/wiki/Sentence_(mathematical_logic)

    In mathematical logic, a sentence (or closed formula) [1] of a predicate logic is a Boolean-valued well-formed formula with no free variables.A sentence can be viewed as expressing a proposition, something that must be true or false.

  3. Open formula - Wikipedia

    en.wikipedia.org/wiki/Open_formula

    An open formula is a formula that contains at least one free variable. [citation needed] An open formula does not have a truth value assigned to it, in contrast with a closed formula which constitutes a proposition and thus can have a truth value like true or false. An open formula can be transformed into a closed formula by applying a ...

  4. Open problem - Wikipedia

    en.wikipedia.org/wiki/Open_problem

    Two notable examples in mathematics that have been solved and closed by researchers in the late twentieth century are Fermat's Last Theorem [1] and the four-color theorem. [2] [3] An important open mathematics problem solved in the early 21st century is the Poincaré conjecture. Open problems exist in all scientific fields.

  5. Millennium Prize Problems - Wikipedia

    en.wikipedia.org/wiki/Millennium_Prize_Problems

    The Clay Mathematics Institute officially designated the title Millennium Problem for the seven unsolved mathematical problems, the Birch and Swinnerton-Dyer conjecture, Hodge conjecture, Navier–Stokes existence and smoothness, P versus NP problem, Riemann hypothesis, Yang–Mills existence and mass gap, and the Poincaré conjecture at the ...

  6. Propositional calculus - Wikipedia

    en.wikipedia.org/wiki/Propositional_calculus

    Propositional logic deals with statements, which are defined as declarative sentences having truth value. [ 26 ] [ 1 ] Examples of statements might include: Wikipedia is a free online encyclopedia that anyone can edit.

  7. Proposition - Wikipedia

    en.wikipedia.org/wiki/Proposition

    In both instances, the statement is true, but means something different. These problems are addressed in predicate logic by using a variable for the problematic term, so that “X is a philosopher” can have Socrates or Plato substituted for X, illustrating that “Socrates is a philosopher” and “Plato is a philosopher” are different ...

  8. Mathematical proof - Wikipedia

    en.wikipedia.org/wiki/Mathematical_proof

    Presenting many cases in which the statement holds is not enough for a proof, which must demonstrate that the statement is true in all possible cases. A proposition that has not been proved but is believed to be true is known as a conjecture, or a hypothesis if frequently used as an assumption for further mathematical work.

  9. List of conjectures - Wikipedia

    en.wikipedia.org/wiki/List_of_conjectures

    A consequence of the classification of finite simple groups, completed in 2004 by the usual standards of pure mathematics. 2004: Adam Marcus and Gábor Tardos: Stanley–Wilf conjecture: permutation classes: Marcus–Tardos theorem 2004: Ualbai U. Umirbaev and Ivan P. Shestakov: Nagata's conjecture on automorphisms: polynomial rings: 2004