The Pythagorean theorem restated in squared distance

Identifier: F:cpoint-pythagoras-distsq
Proof route: kernel-lean
External status: proved
Axiom footprint: Empty

Recorded description

The same hypothesis as F:cpoint-pythagoras (legs at c perpendicular) gives distSq(a,b) CReal.Equiv-equivalent to distSq(a,c) + distSq(b,c) -- the same theorem in the distSq vocabulary F:cpoint-parallelogram-law and F:cpoint-stewart use, rather than raw dot products.

Formal statement

theorem CPoint.pythagoras_distSq : ((x0 : CPoint) -> ((x1 : CPoint) -> ((x2 : CPoint) -> ((x3 : CReal.Equiv (CPoint.dot (CPoint.sub x0 x2) (CPoint.sub x1 x2)) CReal.zero) -> CReal.Equiv (CPoint.distSq x0 x1) (CReal.add (CPoint.distSq x0 x2) (CPoint.distSq x1 x2))))))

Dependencies

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1 direct dependencies 0 direct dependents

Evidence

kernel-CPoint.pythagoras_distSq

Kind: kernel-term
Status: checked

Supports: CPoint.pythagoras_distSq is admitted by the trusted kernel gate with the type recorded in formal.statement.

Checker command

cargo run -q --release -p axeyum-lean-kernel --example theorem_dependency_inventory -- CPoint.pythagoras_distSq 2>/dev/null | grep -cE '^CPoint\.pythagoras_distSq[[:space:]]'

Evidence notes

`build_cpoint_prelude` admits CPoint.pythagoras_distSq through the trusted `Kernel::add_declaration` gate, which re-checks the proof term against the stated type, so a line in this tool's output for the exact name is a machine-checked proof having been admitted. `theorem_dependency_inventory` builds creal/complex/cpoint (extended 2026-08-25); it exits non-zero for a named filter that matches nothing, and `grep -c` (never `-q`) independently asserts the exact tab-anchored line is present. `--release` is MANDATORY: building the constructed carriers recurses deep enough in a debug build to overflow the default thread stack (measured on this tree: release exits 0, debug SIGABRTs at 134) -- the same resource-limit gotcha documented for `prelude_theorem_inventory --include-constructed`.

footprint-CPoint.pythagoras_distSq

Kind: exhaustive-enumeration
Status: checked

Supports: axiom_footprint: [] -- CPoint.pythagoras_distSq's narrow AND widened trusted-declaration closure is empty

Checker command

cargo run -q --release -p axeyum-lean-kernel --example footprint_closure_audit -- --include-constructed 2>/dev/null | grep -cE '^cpoint[[:space:]]CPoint\.pythagoras_distSq[[:space:]][^[:space:]]*[[:space:]]0[[:space:]][[:space:]][[:space:]]0[[:space:]]$'

Evidence notes

`nat_axiom_inventory` does NOT cover `cpoint` at all (verified: `--include-constructed --require-axiom-free cpoint` errors '"cpoint" is not enumerated by this run (known: ... creal, complex)' -- cpoint was never added to that tool's group list, an empty/absent-coverage trap in its own right). `footprint_closure_audit --include-constructed` DOES build a `cpoint` group (verified in its `build_groups`) and, per admitted theorem, emits a row `cpoint<TAB>NAME<TAB>narrow_kinds<TAB>narrow_dangling<TAB>narrow_trusted<TAB>widened_trusted<TAB>widened_dangling<TAB>inductive_edge_diffs`. An axiom-free theorem has narrow_dangling=0, narrow_trusted empty, widened_trusted empty (the WIDENED closure additionally walks inductive constructor/recursor types one step further than `render_deps`, so this is stronger than the narrow-only check the `nat_axiom_inventory`-style facts use), widened_dangling=0, and no inductive edge diff -- the anchored regex below requires all of that in one line. `--include-constructed` is REQUIRED: without it the cpoint group is never built and BOTH the row-match and the `cpoint: theorems=` coverage line are absent (verified: 0 matches for either, vs 1 for both with the flag), which is the same coverage trap CLAUDE.md already documents for `nat_axiom_inventory`. `--release` is MANDATORY for the same deep-recursion reason as `theorem_dependency_inventory` (this tool's own doc example uses it); measured full-audit wall time on this tree ~20s release.

Provenance

{
  "date": "2026-08-25",
  "established_by": "axeyum-lean-kernel build_cpoint_prelude",
  "source": "theorem name and dependency edges from theorem_dependency_inventory (builds creal/complex/cpoint); canonical type read via a standalone probe binary depending on axeyum-lean-kernel by path, calling only its public Kernel API (environment(), display_name(), render_lean(), axiom_footprint()) -- no in-tree example prints Complex/CPoint theorem types; crates/ source was not touched to produce this batch."
}