Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
- Let be a field, let be a natural number with successor map as in that definition, let be the initial segment determined by , and let be a map, whose value at is written . Let be the map given by…
The Induced Norm is a Norm, and Induces a Metric
lemmalem:inner-product-norm-is-norm-2026aAnalysisLinear AlgebraLet together with be a complex inner product space, let be the norm induced by the inner product, and write with the additive inverse of Elementary Identities in a Vector Space. Then the following hold.…- Let together with be a complex inner product space and let . By condition 4 of Complex Inner Product Space the number is a real number with . The norm induced by the inner product assigns to …
- Let be a complex vector space with zero vector , and for a complex number let denote its modulus. A norm on is a map assigning to each a real number , subject to the following conditions for all and all com…
Cauchy-Schwarz Inequality in a Complex Inner Product Space
theoremthm:cauchy-schwarz-complex-2026aAnalysisLinear AlgebraLet together with be a complex inner product space and let . Then, with the modulus of a complex number, an inequality between real numbers, the two facto…Elementary Properties of a Complex Inner Product
lemmalem:inner-product-elementary-properties-2026aAnalysisLinear AlgebraLet together with be a complex inner product space, let be its zero vector, let , and let be a complex number with conjugate . Then the following hold. 1. (Additivity in the first argument)…- Let be the field of complex numbers, let be a complex vector space, let be its zero vector, and for let denote its complex conjugate. An inner product on is a map assigning to each pair of elements of…
Linear Maps, Linear Operators and Isomorphisms of Vector Spaces
definitiondef:linear-map-2026bAlgebraLinear AlgebraA linear map between vector spaces over the same field preserves sums and scalar multiples; a linear operator is a linear map from a space to itself, and an isomorphism is a bijective linear map.- A linear subspace of a vector space is a subset containing the zero vector and closed under addition and scalar multiplication.
Elementary Identities in a Vector Space
lemmalem:vector-space-basic-identities-2026cAlgebraLinear AlgebraIn a vector space: cancellation, 0v = 0, a multiple of the zero vector is zero, negatives as multiples by -1, negatives of negatives and of sums, the rules for differences, and no zero divisors.- A vector space over a field K is a set with an addition and a scalar multiplication satisfying the eight usual axioms; a real vector space is a vector space over the real numbers.
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 .