Lax Lean Archive

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Proof of `Averaging outside a set of coordinates` (2nd statement)

groundedproofs/Lax253009Proofs/FourierProjection.lean · lax-253009

What this proof establishes

thm✓Lax253009.FourierProjection (2nd statement)

Assuming the claims on the left, the claim on the right holds — checked by the archive's pipeline. Proof code is not displayed here.

Read the Lean proof on GitHub

Description

Expand F in characters. Averaging kills a character with any coordinate outside U; orthogonality then extracts the remaining coefficient.