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  2. Ordinal arithmetic - Wikipedia

    en.wikipedia.org/wiki/Ordinal_arithmetic

    The natural product is associative and commutative and distributes over the natural sum. The natural product is always greater or equal to the usual product, but it may be strictly greater. For example, the natural product of ω and 2 is ω · 2 (the usual product), but this is also the natural product of 2 and ω. Under natural addition, the ...

  3. Aleph number - Wikipedia

    en.wikipedia.org/wiki/Aleph_number

    the set of natural numbers, irrespective of including or excluding zero, the set of all integers, any infinite subset of the integers, such as the set of all square numbers or the set of all prime numbers, the set of all rational numbers, the set of all constructible numbers (in the geometric sense), the set of all algebraic numbers,

  4. Set-theoretic definition of natural numbers - Wikipedia

    en.wikipedia.org/wiki/Set-theoretic_definition...

    Definition: the sum of cardinals K and L such as K= Card(A) and L = Card(B) where the sets A and B are disjoint, is Card (A ∪ B). The definition of a finite set is given independently of natural numbers: [3] Definition: A set is finite if and only if any non empty family of its subsets has a minimal element for the inclusion order.

  5. List of trigonometric identities - Wikipedia

    en.wikipedia.org/wiki/List_of_trigonometric...

    Ptolemy's theorem states that the sum of the products of the lengths of opposite sides is equal to the product of the lengths of the diagonals. When those side-lengths are expressed in terms of the sin and cos values shown in the figure above, this yields the angle sum trigonometric identity for sine: sin(α + β) = sin α cos β + cos α sin β.

  6. Glossary of set theory - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_set_theory

    A set whose elements can be put into a one-to-one correspondence with the set of natural numbers, making it countable. enumeration The process of listing or counting elements in a set, especially for countable sets. epsilon 1. An epsilon number is an ordinal α such that α=ω α 2. Epsilon zero (ε 0) is the smallest epsilon number equinumerous

  7. Transcendental number theory - Wikipedia

    en.wikipedia.org/wiki/Transcendental_number_theory

    where all four unknowns are algebraic, the αs being neither zero nor one and the βs being irrational. Finding similar lower bounds for the sum of three or more logarithms had eluded Gelfond, though. The proof of Baker's theorem contained such bounds, solving Gauss' class number problem for class number one in the process.

  8. Law of tangents - Wikipedia

    en.wikipedia.org/wiki/Law_of_tangents

    In the time before electronic calculators were available, this method was preferable to an application of the law of cosines c = √ a 2 + b 2 − 2ab cos γ, as this latter law necessitated an additional lookup in a logarithm table, in order to compute the square root.

  9. Mollweide's formula - Wikipedia

    en.wikipedia.org/wiki/Mollweide's_formula

    In trigonometry, Mollweide's formula is a pair of relationships between sides and angles in a triangle. [1] [2]A variant in more geometrical style was first published by Isaac Newton in 1707 and then by Friedrich Wilhelm von Oppel [] in 1746.