Alphabeta Math
LemmaStatement: AI-adaptedProof: AI-generatedprecheck passaudited 2026-08-21
How statement and proof provenance work

The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.

  • Literature-sourced: the exact statement appears in a cited source; only wording and notation differ.
  • AI-adapted: a semantically identical restatement of literature-sourced material, modulo indexing, notation, and boundary cases adopted by the library.
  • AI-generated: a genuinely novel statement formulated by AI, with no source for the claim itself.

These labels describe origin, not correctness: citations and verification chips remain separate evidence.

Matrix inversion preserves Ck regularity where the determinant is nonzero

Statement

Let m,n≥1, let U⊆Rm be open, and let r∈N. If the entries of A:U→Mn(R) are Cr and det⁡A never vanishes, then the entries of A−1 are Cr.

Facts & Assumptions

[L1]

For an invertible square matrix, A−1=det⁡(A)−1adj⁡(A). (If det⁡(A) is a unit, then A−1=det⁡(A)−1adj⁡(A))

[L2]

The function det⁡:Mn(R)→R is evaluation of the polynomial ∑σ∈Snsgn⁡(σ)x1,σ(1)⋯xn,σ(n). (For every fixed finite size at least one, the determinant of a real square matrix is a polynomial in its matrix entries)

[L3]

Finite componentwise sums and products of Ck Euclidean maps are Ck, and a composite of composable Ck Euclidean maps is Ck (Ck Euclidean maps are closed under componentwise algebra and composition).

Proof

technique · direct
1.1L1L2L3

Every cofactor and the determinant are polynomial expressions in the Cr entries of A, so they are Cr by [L2] and [L3]; [L1] identifies the only remaining factor needed for the inverse.

1.2givenalgebra

On R∖{0}, repeated differentiation of h(t)=t−1 gives h(j)(t)=(−1)jj!t−j−1. This formula follows by induction from the reciprocal and product rules, and every derivative displayed is continuous on that domain.

2.1step 1.1step 1.2L1L3∎

Since det⁡A never vanishes, its image lies in the domain of step 1.2. Thus (det⁡A)−1 is Cr by composition, and [L1] together with step 1.1 and [L3] makes every entry of A−1 Cr.

Depends on

Used by

Dependency tree · two levels

34 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.

Sources