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  2. Converse (logic) - Wikipedia

    en.wikipedia.org/wiki/Converse_(logic)

    For example, the four-vertex theorem was proved in 1912, but its converse was proved only in 1997. [3] In practice, when determining the converse of a mathematical theorem, aspects of the antecedent may be taken as establishing context. That is, the converse of "Given P, if Q then R" will be "Given P, if R then Q".

  3. Converse relation - Wikipedia

    en.wikipedia.org/wiki/Converse_relation

    For example, the converse of the relation 'child of' is the relation 'parent of'. In formal terms, if X {\displaystyle X} and Y {\displaystyle Y} are sets and L ⊆ X × Y {\displaystyle L\subseteq X\times Y} is a relation from X {\displaystyle X} to Y , {\displaystyle Y,} then L T {\displaystyle L^{\operatorname {T} }} is the relation defined ...

  4. Contraposition - Wikipedia

    en.wikipedia.org/wiki/Contraposition

    Conversion (the converse), "If I wear my coat, then it is raining ." The converse is actually the contrapositive of the inverse, and so always has the same truth value as the inverse (which as stated earlier does not always share the same truth value as that of the original proposition).

  5. Relation (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Relation_(mathematics)

    For example, "is a blood relative of" is a symmetric relation, because x is a blood relative of y if and only if y is a blood relative of x. Antisymmetric for all x, y ∈ X, if xRy and yRx then x = y. For example, ≥ is an antisymmetric relation; so is >, but vacuously (the condition in the definition is always false). [11] Asymmetric

  6. Relation algebra - Wikipedia

    en.wikipedia.org/wiki/Relation_algebra

    In mathematics and abstract algebra, a relation algebra is a residuated Boolean algebra expanded with an involution called converse, a unary operation.The motivating example of a relation algebra is the algebra 2 X 2 of all binary relations on a set X, that is, subsets of the cartesian square X 2, with R•S interpreted as the usual composition of binary relations R and S, and with the ...

  7. List of logic symbols - Wikipedia

    en.wikipedia.org/wiki/List_of_logic_symbols

    The following table lists many common symbols, together with their name, how they should be read out loud, and the related field of mathematics. Additionally, the subsequent columns contains an informal explanation, a short example, the Unicode location, the name for use in HTML documents, [1] and the LaTeX symbol.

  8. If and only if - Wikipedia

    en.wikipedia.org/wiki/If_and_only_if

    The corresponding logical symbols are "", "", [6] and , [10] and sometimes "iff".These are usually treated as equivalent. However, some texts of mathematical logic (particularly those on first-order logic, rather than propositional logic) make a distinction between these, in which the first, ↔, is used as a symbol in logic formulas, while ⇔ is used in reasoning about those logic formulas ...

  9. Inverse relation - Wikipedia

    en.wikipedia.org/wiki/Inverse_relation

    In mathematics, inverse relation may refer to: Converse relation or "transpose", in set theory; Negative relationship, in statistics; Inverse proportionality; Relation between two sequences, expressing each of them in terms of the other