Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
- Let be a field, with additive identity and multiplicative identity . A vector space over is a set together with two operations: an addition, assigning to each pair of elements of an element of , and a scalar multiplication, assigning to each…
Canonical Form and Arithmetic of Complex Numbers
lemmalem:complex-canonical-form-2026aAnalysisAlgebraLet be the field of complex numbers with imaginary unit , and let be the set of real numbers. Then the following hold. 1. (Identities and inverses of real numbers) The additive identity of is the real number and the multiplicative id…Existence and Uniqueness of the Complex Numbers
theoremthm:complex-numbers-existence-uniqueness-2026aAnalysisAlgebraLet be the set of real numbers, with its addition, its multiplication and its order. Call a pair , consisting of a field and an element , a complex pair if the following three conditions hold, where and denote the addition and multipli…Properties of Complex Conjugation and Modulus
lemmalem:complex-conjugate-modulus-properties-2026aAnalysisAlgebraLet be the field of complex numbers with imaginary unit , let be the set of real numbers, and let . Sums, products and inverses are those of the field , and abbreviates ; for a real number , abbrevia…- Let be the field of complex numbers, let , and let and be its real and imaginary parts. The modulus of , written , is the unique real number with and ; such an …
- Let be the field of complex numbers with imaginary unit , let , and let and be its real and imaginary parts. The complex conjugate of is the complex number…
Real and Imaginary Parts of a Complex Number
definitiondef:complex-real-imaginary-part-2026aAnalysisAlgebraLet be the field of complex numbers with imaginary unit , and let . By claim 3 of Canonical Form and Arithmetic of Complex Numbers there is exactly one pair of real numbers with . The real part of is the real number…Existence and Uniqueness of the Square Root of a Sum of Two Squares
lemmalem:sum-two-squares-square-root-2026aAnalysisLet and be real numbers. Then , and there is exactly one real number with and .- Let be the set of real numbers, with its addition and multiplication. The complex numbers are a field , whose addition and multiplication are written and (the product being also written ), together with a distinguished element…
- Let , where is the set of natural numbers with multiplication as in that definition. We say that divides , written if there exists with .
- A set is called finite if or if has elements for some natural number .
Properties of the Order on the Natural Numbers
lemmalem:order-natural-numbers-2026aNumber TheorySet TheoryLet be the set of natural numbers, with addition and successor map as in that definition, and let and be the order relations of that definition. Then the following hold for all . 1. ; if then ; if…- Let be the set of natural numbers, with addition as in that definition, and let . We write if there exists with , and we write if or . We also write for , and for…
Arithmetic of Addition on the Natural Numbers
lemmalem:natural-number-addition-2026aNumber TheorySet TheoryLet be the set of natural numbers, with addition and successor map as in that definition. Then the following hold for all . 1. and . 2. . 3. (Associativity) . 4. (Commutativity)…Principle of Induction for the Natural Numbers
axiomaxiom:induction-natural-numbers-2026aLogicSet TheoryLet be the set of natural numbers, with successor map as in that definition. We take as an axiom the following principle of induction. If satisfies 1. , and 2. for every , then .- Let , , and be sets. 1. Every bijection is injective; that is, implies for all . 2. If and are bijections, then the map defined by is a bijection. 3. If is a bijection…
- Let be a group whose underlying set is finite, and let be a subgroup of . Then the following hold. 1. The sets and , where is the set of left cosets of in , are finite and nonempty, and where is the order of …
Left Cosets Partition a Group and All Have the Same Cardinality
theoremthm:coset-partition-2026aAlgebraLet be a group, written multiplicatively, with identity element and inverses as in Uniqueness of the Identity Element and of Inverses in a Group, and let be a subgroup of . For let be the left coset determined by . Then for all…Left Coset, Order of a Group, and Index of a Subgroup
definitiondef:left-coset-order-index-2026aAlgebraLet be a group, written multiplicatively as , and let be a subgroup of . For , the left coset of determined by is the subset of given by The collection of all left cosets of in is denoted…- Let be the set of natural numbers with successor map , let be the order on , let denote the initial segment determined by , and let the notions number of elements and finite be as in those definitions. Then the following hold. 1.…