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CorollaryStatement: Literature-sourcedProof: AI-adaptedSession-authored (Fable 5 assisted)precheck passaudited 2026-08-16
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Every finite-dimensional real or complex inner product space has an orthonormal basis

Statement

Every finite-dimensional real or complex inner product space has an orthonormal basis. In dimension zero, this is the empty basis.

Facts & Assumptions

Given: A finite-dimensional inner product space V.

[L1]

A finite-dimensional vector space has a finite basis, with the empty list serving when V=0 (Basis of a vector space: a linearly independent spanning subset; and ordered basis: an injective finite list whose image is a basis).

[L2]

Gram–Schmidt converts every finite independent list into an orthonormal list with the same span (Gram–Schmidt turns every finite independent list into an orthonormal list with the same successive spans).

Proof

technique · direct
1.1

Choose a finite basis (v0,,vr1) of V using [L1].

L1choose
2.1

Apply [L2]. The resulting orthonormal list has the same span as the basis, namely V, and therefore is an orthonormal basis. This also covers r=0.

step 1.1L2

Depends on

Used by

Dependency tree · next 3 levels

Direct dependencies and their dependencies through the next three levels: 53 results over 20 levels. An arrow runs from a result to what uses it, and this result sits at the bottom with a heavier outline. Click the chart to enlarge it.

Sources