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← Session 21 — Tier ii′ planning + launch: close SfBoundProp in Lean (D-064)

#957 assistant 2026-08-21 21:34:07.414 UTC · 675→3524 tok open ⤢
thinking (10227 chars)
Multiple type issues: 1. `hasDerivAt_add_const_I`: the `.add` application — HasDerivAt.add (hf : HasDerivAt f f' x) (hg : HasDerivAt g g' x) : HasDerivAt (f+g) (f'+g') x — the issue: `hid.add hconst` — hid : HasDerivAt id 1 x — the dot `.add` — hid's type: HasDerivAt id 1 x — hmm, hasDerivAt_id returns `HasDerivAt id 1 x`? — maybe it's `hasDerivAt_id (x) : HasDerivAt id 1 x` ✓. hconst : HasDerivAt (fun _ => y*I) 0 x — the application fails with hconst expected `?m.54 ?m.56 x` — meaning the dot-projection `.add` resolved weirdly. Use explicit: `HasDerivAt.add hid hconst` — hmm same. The issue might be `hasDerivAt_id x` — check: `hasDerivAt_id (x : 𝕜) : HasDerivAt id 1 x` ✓ standard. And `.add` — `HasDerivAt.add (hf : HasDerivAt f f' x) (hg : HasDerivAt g g' x) : HasDerivAt (fun x => f x + g x) (f' + g') x` ✓. So `hid.add hconst : HasDerivAt (fun x => x + y*I) (1 + 0) x` ✓ then `convert this using 1; simp`. The error at 40:18 "has type HasDerivAt (fun x => ↑y * I) 0 x but is expected HasDerivAt ?m.54 ?m.56 x" — the ?m.54 unresolved — because `hid.add hconst` — Lean couldn't determine f/f' from hid (id)? Maybe hasDerivAt_id's result is `HasDerivAt id 1 x` — f := id, f' := 1 ✓ concrete... The `?m` suggests elaboration order issue — use explicit HasDerivAt.add hid hconst with named form: ``` have h := HasDerivAt.add (hasDerivAt_id x) (hasDerivAt_const x (y * I)) simpa using h ``` h : HasDerivAt (fun x => id x + (fun _ => y*I) x) (1 + 0) x = HasDerivAt (fun x => x + y*I) (1+0) x — simpa (1+0 = 1, id x = x) ✓. 2. `(hasDerivAt_id y).mul_const I` — mul_const expects a scalar of the same field — y : ℝ! hasDerivAt_id y is for y : ℝ (the identity on ℝ) — I need the identity on ℂ? No wait — in hasDerivAt_const_add_I, the parametrization is over ℝ (y : ℝ) but the map is t ↦ x + t·I : ℝ → ℂ. HasDerivAt here is for ℝ → ℂ maps (real derivative of a complex-valued function). hasDerivAt_id y : HasDerivAt id 1 y — over which field? HasDerivAt for functions between normed spaces over ℝ? The generic HasDerivAt is for functions 𝕜 → F over 𝕜 (same field). For ℝ → ℂ, the derivative is the real derivative: HasDerivAt (fun t : ℝ => t * I) I y — t*I : ℂ with t : ℝ — this is t ↦ Complex.ofReal t * I — the derivative is I as a complex number: HasDerivAt (fun t : ℝ => t * I) I y — provable via `HasDerivAt.mul_const`? hasDerivAt_id y is ℝ→ℝ. I need `(fun t : ℝ => t) ` composed with ofReal then * I: t ↦ (t : ℂ): HasDerivAt (fun t : ℝ => (t : ℂ)) 1 y — `Complex.hasDerivAt_ofReal`? or via ofRealCLM. Then (fun t => (t:ℂ) * I): HasDerivAt (fun t => (t:ℂ) * I) (1 * I) y via .mul_const — mul_const for ℂ-valued over... hmm — HasDerivAt.mul_const : HasDerivAt f f' x → HasDerivAt (fun x => f x * c) (f' * c) x — for f : ℝ → ℂ with c : ℂ ✓ works (real derivative of complex function): f' : ℂ. So: ``` have h1 : HasDerivAt (fun t : ℝ => (t : ℂ)) 1 y := by -- via ofReal: Complex.ofRealCLM derivative exact Complex.hasDerivAt_ofReal? ``` Hmm — let me check what's available: `Complex.hasDerivAt_ofReal`? There's `hasDerivAt_ofReal`? The CLM: `Complex.ofRealCLM : ℝ →L[ℝ] ℂ` — `ContinuousLinearMap.hasDerivAt (f : E →L[𝕜] F) : HasDerivAt f f x` ✓ — ofRealCLM's derivative is ofRealCLM itself = (· * 1)... (ofRealCLM) t = ↑t: HasDerivAt (fun t => ↑t) (ofRealCLM) y where ofRealCLM as a derivative value: HasDerivAt f (f' : F) — for linear maps, HasDerivAt f (f) x with f' = f (the CLM applied)... hmm the HasDerivAt's f' for a CLM L is L 1 = ofReal 1 = 1: ``` have hof : HasDerivAt (fun t : ℝ => (t : ℂ)) 1 y := by have h := Complex.ofRealCLM.hasDerivAt (x := y) simpa using h ``` `ContinuousLinearMap.hasDerivAt : HasDerivAt f f x` — f's derivative is f itself as a continuous linear map — for ofRealCLM: HasDerivAt ofRealCLM ofRealCLM y — and ofRealCLM 1 = 1 — `simpa using h` should give HasDerivAt (↑·) 1 y. Then h1 : HasDerivAt (fun t => (t:ℂ) * I) (1 * I) y := (hof).mul_const I — then simplify 1*I = I. Then hconst.add h1: HasDerivAt (fun t => x + t*I) (0 + I) y ✓. Wait — but mul_const for the ℂ-valued map: `HasDerivAt.mul_const (hf : HasDerivAt f f' x) (c : ℂ) : HasDerivAt (fun x => f x * c) (f' * c) x` — for f : ℝ → ℂ, c : ℂ ✓. Hmm — actually check: hasDerivAt_id y with y : ℝ gives HasDerivAt id 1 y — and earlier I used `(hasDerivAt_id y).mul_const I` — the error "argument I has type ℂ but expected ℝ" — because hasDerivAt_id y was the ℝ identity and mul_const wanted a real scalar. Right. 3. `MapsTo` unknown identifier — need `Set.MapsTo` qualified or `open Set`. The vendored file has `open ... Set`? My file has `open Zeta23 Complex Filter Topology` — MapsTo is `Set.MapsTo`. Add `Set` to opens or qualify. The vendored MapsTo lemmas use unqualified `MapsTo` — they're stated in namespace Zeta23 with Set open. In my file: qualify `Set.MapsTo` in the hypotheses, but the vendored lemma names (mapsTo_rectangleBorder_left_im) produce `MapsTo` — I can write `Set.MapsTo` in my statements and apply the vendored lemmas (same thing). Add `open Set` to the file opens — simplest. Hmm — `open Set` might shadow other things (Set.Icc vs...). The vendored file uses `open Complex Set Topology Filter Asymptotics Real`. I'll add `Set` to my opens. 4. `h2` application type mismatch in HIntegral_deriv (line 65): `h1.comp x h2` — h1 : HasDerivAt G (deriv G (x+y*I)) (x+y*I) — h2 : HasDerivAt (fun x => x + y*I) 1 x — HasDerivAt.comp (hg : HasDerivAt g g' (f x)) (hf : HasDerivAt f f' x) : HasDerivAt (g ∘ f) (g' * f') x — h1.comp x h2 — wait the signature: `HasDerivAt.comp (hg : HasDerivAt g g' (f x)) (hf : HasDerivAt f f' x) : HasDerivAt (g ∘ f) (g' * f') x` — application: h1.comp x h2 ✓ standard form (comp takes x explicitly). The error: h2 "has type HasDerivAt (fun x => x + ↑y * I) 1 ↑x but expected ?m.183 ?m.185 x" — the `↑x` — h2's point is ↑x (cast) vs x — hasDerivAt_add_const_I y x : HasDerivAt (fun t => t + y * I) 1 x — x : ℝ ✓ — the display shows ↑x — the elaboration lifted x into ℂ?? — because in `h1.comp x h2`, comp expects hf : HasDerivAt f f' x with f : ? → ? and g at (f x): h1's point is (x + y * I) : ℂ — so f x = x + y*I needs x coerced to ℂ — Lean inferred f : ℂ → ℂ and x : ℂ, casting my x : ℝ to ↑x. But the inner parametrization is over ℝ! The HasDerivAt.comp for g : ℂ → ℂ and f : ℝ → ℂ — mixed-field composition is NOT HasDerivAt.comp (which needs same field!). PROBLEM: the chain rule for g ∘ f with f : ℝ → ℂ and g : ℂ → ℂ — the fields differ (ℝ for the real parameter, ℂ for g's holomorphic derivative). The composition's derivative is g'(f(x))·f'(x) as a complex number — the relevant lemma: `HasDerivAt.comp` requires g : 𝕜 → 𝕜 over the same 𝕜. For mixed: there's `HasDerivAt.comp_of_real`? or `HasDerivAt.comp'`? Hmm — actually for f : ℝ → ℂ differentiable (real derivative) and g : ℂ → ℂ holomorphic (complex derivative): the composition f(t) path in ℂ: (g∘f)'(t) = g'(f(t))·f'(t) — this is `HasDerivAt.comp` with 𝕜 = ... no. There should be a lemma for real-parameter curves into complex functions: `HasDerivAt.comp` doesn't apply; but there's `HasDerivAt.comp_hasDerivAt`? or use `HasFDerivAt.comp` with different scalars?? Hmm — actually the standard trick: g analytic ⟹ its real derivative along the path: use `HasDerivAt.comp` where BOTH are over ℝ? g's complex derivative gives the real derivative along any real-direction: HasDerivAt g (g' • (1 : ℂ)) — as a real-linear map: g is ℝ-differentiable with derivative (z ↦ g'·z): so the composition: HasFDerivAt-style. The cleanest Mathlib lemma: `HasDerivAt.comp` is for same-field. For mixed: `HasDerivAt.comp_ofReal`? Hmm. Alternative: `HasDerivAt.comp` exists in two flavors... Let me think about what the vendored PNT+ code does for parametrized sides — they must have faced this. Actually — the standard Mathlib lemma for this: `HasDerivAt.comp` with signature `(hg : HasDerivAt g (g') (f x)) (hf : HasDerivAt f (f') x) : HasDerivAt (g ∘ f) (g' * f') x` — fields: f : 𝕜 → F, g : F → F'... HasDerivAt is defined for functions between normed spaces over the SAME field 𝕜. For f : ℝ → ℂ and g : ℂ → ℂ: g is differentiable over ℂ; the composition over ℝ — the chain rule works with g's ℂ-derivative restricted to a real-linear map: the relevant instance: g is also ℝ-differentiable (DifferentiableAt ℂ g s → DifferentiableAt ℝ g s? — `DifferentiableAt.restrict_scalars`! There's `DifferentiableAt.restrict_scalars (h : DifferentiableAt ℂ f x) : DifferentiableAt ℝ f x` ✓ exists in Mathlib for restricted scalars. And then HasFDerivAt.comp for ℝ maps. The HasDerivAt (1-dimensional) version: `HasDerivAt.restrict_scalars`? Hmm. This is getting heavy. Alternative cleaner approach for the side FTCs: AVOID the mixed-field chain rule by using `HasFDerivAt.comp` with CLMs? — or sidestep entirely: note that for our specific G (rational functions of (w−1)), the side integrands' antiderivatives are explicit — the FTC needs (x ↦ G(x+yI))' = G'(x+yI): prove it via `HasDerivAt.scomp`? Hmm. Actually — the RIGHT Mathlib lemma: `HasDerivAt.comp` does exist in a version for f : 𝕜 → F, g : F → F' over the same field 𝕜... For f : ℝ → ℂ (𝕜 = ℝ, F = ℂ) and g : ℂ → ℂ (𝕜 = ℂ) — different fields. The composition's derivative over ℝ: need g ℝ-differentiable. `HasDerivAt.comp` in Mathlib is stated for g over the SAME 𝕜 as f. There's `HasDerivAt.comp` and `HasDerivAt.comp_hasDerivAt`... The cleanest available: `HasFDerivAt.comp` (Fréchet, any normed spaces over the same field ℝ): G's HasFDerivAt (as a ℂ-differentiable function, restrict scalars to ℝ) with derivative the CLM (z ↦ G'·z); the path γ(x) = x + yI has HasFDerivAt with derivative (t ↦ t·1). Chain: (G∘γ)' = (z ↦ G'·z) ∘ (t ↦ t·1) = (t ↦ G'·t·1) = (t ↦ G'·t): so HasFDerivAt (G∘γ) (t ↦ G'·t) x — then to HasDerivAt: the 1-dim HasDerivAt from HasFDerivAt via `HasFDerivAt.hasDerivAt`? — for functions into ℂ over ℝ, HasDerivAt f f' x ⟺ HasFDerivAt f (f' • (1:ℝ→L[ℝ]ℂ))... there's `hasDerivAt_iff_hasFDerivAt`? Simplest robust hack: use `HasDerivAt.comp` with g viewed as a real function via restrict_scalars at the HasDerivAt level. Is there `HasDerivAt.restrict_scalars`? Let me grep. Actually — maybe easier: there IS a mixed composition lemma `HasDerivAt.comp` in Mathlib for this exact case? Let me grep for comp variants.
The mixed-field chain rule needs the right lemma. Let me check what's available.
tool: Bash
input
{
  "command": "cd /d/Python/Quantum/zeta-23-lean/.lake/packages/mathlib && grep -rn \"theorem HasDerivAt.restrict_scalars\\|lemma HasDerivAt.restrict_scalars\\|restrict_scalars.*HasDerivAt\" Mathlib/ --include=*.lean | head -4; grep -rn \"hasDerivAt_ofReal\\|ofRealCLM\" Mathlib/Analysis/Complex/Basic.lean | head -5; grep -rn \"theorem HasDerivAt.comp\\b\" Mathlib/Analysis/Calculus/Deriv/Comp.lean | head -3",
  "description": "Find restrict_scalars and composition lemmas for mixed fields"
}
raw content_json (database row)
[{"type":"thinking","thinking":"Multiple type issues:\n\n1. `hasDerivAt_add_const_I`: the `.add` application — HasDerivAt.add (hf : HasDerivAt f f' x) (hg : HasDerivAt g g' x) : HasDerivAt (f+g) (f'+g') x — the issue: `hid.add hconst` — hid : HasDerivAt id 1 x — the dot `.add` — hid's type: HasDerivAt id 1 x — hmm, hasDerivAt_id returns `HasDerivAt id 1 x`? — maybe it's `hasDerivAt_id (x) : HasDerivAt id 1 x` ✓. hconst : HasDerivAt (fun _ => y*I) 0 x — the application fails with hconst expected `?m.54 ?m.56 x` — meaning the dot-projection `.add` resolved weirdly. Use explicit: `HasDerivAt.add hid hconst` — hmm same. The issue might be `hasDerivAt_id x` — check: `hasDerivAt_id (x : 𝕜) : HasDerivAt id 1 x` ✓ standard. And `.add` — `HasDerivAt.add (hf : HasDerivAt f f' x) (hg : HasDerivAt g g' x) : HasDerivAt (fun x => f x + g x) (f' + g') x` ✓. So `hid.add hconst : HasDerivAt (fun x => x + y*I) (1 + 0) x` ✓ then `convert this using 1; simp`. The error at 40:18 \"has type HasDerivAt (fun x => ↑y * I) 0 x but is expected HasDerivAt ?m.54 ?m.56 x\" — the ?m.54 unresolved — because `hid.add hconst` — Lean couldn't determine f/f' from hid (id)? Maybe hasDerivAt_id's result is `HasDerivAt id 1 x` — f := id, f' := 1 ✓ concrete... The `?m` suggests elaboration order issue — use explicit HasDerivAt.add hid hconst with named form:\n```\n  have h := HasDerivAt.add (hasDerivAt_id x) (hasDerivAt_const x (y * I))\n  simpa using h\n```\nh : HasDerivAt (fun x => id x + (fun _ => y*I) x) (1 + 0) x = HasDerivAt (fun x => x + y*I) (1+0) x — simpa (1+0 = 1, id x = x) ✓.\n\n2. `(hasDerivAt_id y).mul_const I` — mul_const expects a scalar of the same field — y : ℝ! hasDerivAt_id y is for y : ℝ (the identity on ℝ) — I need the identity on ℂ? No wait — in hasDerivAt_const_add_I, the parametrization is over ℝ (y : ℝ) but the map is t ↦ x + t·I : ℝ → ℂ. HasDerivAt here is for ℝ → ℂ maps (real derivative of a complex-valued function). hasDerivAt_id y : HasDerivAt id 1 y — over which field? HasDerivAt for functions between normed spaces over ℝ? The generic HasDerivAt is for functions 𝕜 → F over 𝕜 (same field). For ℝ → ℂ, the derivative is the real derivative: HasDerivAt (fun t : ℝ => t * I) I y — t*I : ℂ with t : ℝ — this is t ↦ Complex.ofReal t * I — the derivative is I as a complex number: HasDerivAt (fun t : ℝ => t * I) I y — provable via `HasDerivAt.mul_const`? hasDerivAt_id y is ℝ→ℝ. I need `(fun t : ℝ => t) ` composed with ofReal then * I: \n   t ↦ (t : ℂ): HasDerivAt (fun t : ℝ => (t : ℂ)) 1 y — `Complex.hasDerivAt_ofReal`? or via ofRealCLM. Then (fun t => (t:ℂ) * I): HasDerivAt (fun t => (t:ℂ) * I) (1 * I) y via .mul_const — mul_const for ℂ-valued over... hmm — HasDerivAt.mul_const : HasDerivAt f f' x → HasDerivAt (fun x => f x * c) (f' * c) x — for f : ℝ → ℂ with c : ℂ ✓ works (real derivative of complex function): f' : ℂ. So:\n```\n  have h1 : HasDerivAt (fun t : ℝ => (t : ℂ)) 1 y := by\n    -- via ofReal: Complex.ofRealCLM derivative\n    exact Complex.hasDerivAt_ofReal? \n```\nHmm — let me check what's available: `Complex.hasDerivAt_ofReal`? There's `hasDerivAt_ofReal`? The CLM: `Complex.ofRealCLM : ℝ →L[ℝ] ℂ` — `ContinuousLinearMap.hasDerivAt (f : E →L[𝕜] F) : HasDerivAt f f x` ✓ — ofRealCLM's derivative is ofRealCLM itself = (· * 1)... (ofRealCLM) t = ↑t: HasDerivAt (fun t => ↑t) (ofRealCLM) y where ofRealCLM as a derivative value: HasDerivAt f (f' : F) — for linear maps, HasDerivAt f (f) x with f' = f (the CLM applied)... hmm the HasDerivAt's f' for a CLM L is L 1 = ofReal 1 = 1: \n```\n  have hof : HasDerivAt (fun t : ℝ => (t : ℂ)) 1 y := by\n    have h := Complex.ofRealCLM.hasDerivAt (x := y)\n    simpa using h\n```\n`ContinuousLinearMap.hasDerivAt : HasDerivAt f f x` — f's derivative is f itself as a continuous linear map — for ofRealCLM: HasDerivAt ofRealCLM ofRealCLM y — and ofRealCLM 1 = 1 — `simpa using h` should give HasDerivAt (↑·) 1 y.\n\nThen h1 : HasDerivAt (fun t => (t:ℂ) * I) (1 * I) y := (hof).mul_const I — then simplify 1*I = I.\nThen hconst.add h1: HasDerivAt (fun t => x + t*I) (0 + I) y ✓.\n\nWait — but mul_const for the ℂ-valued map: `HasDerivAt.mul_const (hf : HasDerivAt f f' x) (c : ℂ) : HasDerivAt (fun x => f x * c) (f' * c) x` — for f : ℝ → ℂ, c : ℂ ✓.\n\nHmm — actually check: hasDerivAt_id y with y : ℝ gives HasDerivAt id 1 y — and earlier I used `(hasDerivAt_id y).mul_const I` — the error \"argument I has type ℂ but expected ℝ\" — because hasDerivAt_id y was the ℝ identity and mul_const wanted a real scalar. Right.\n\n3. `MapsTo` unknown identifier — need `Set.MapsTo` qualified or `open Set`. The vendored file has `open ... Set`? My file has `open Zeta23 Complex Filter Topology` — MapsTo is `Set.MapsTo`. Add `Set` to opens or qualify. The vendored MapsTo lemmas use unqualified `MapsTo` — they're stated in namespace Zeta23 with Set open. In my file: qualify `Set.MapsTo` in the hypotheses, but the vendored lemma names (mapsTo_rectangleBorder_left_im) produce `MapsTo` — I can write `Set.MapsTo` in my statements and apply the vendored lemmas (same thing). Add `open Set` to the file opens — simplest. Hmm — `open Set` might shadow other things (Set.Icc vs...). The vendored file uses `open Complex Set Topology Filter Asymptotics Real`. I'll add `Set` to my opens.\n\n4. `h2` application type mismatch in HIntegral_deriv (line 65): `h1.comp x h2` — h1 : HasDerivAt G (deriv G (x+y*I)) (x+y*I) — h2 : HasDerivAt (fun x => x + y*I) 1 x — HasDerivAt.comp (hg : HasDerivAt g g' (f x)) (hf : HasDerivAt f f' x) : HasDerivAt (g ∘ f) (g' * f') x — h1.comp x h2 — wait the signature: `HasDerivAt.comp (hg : HasDerivAt g g' (f x)) (hf : HasDerivAt f f' x) : HasDerivAt (g ∘ f) (g' * f') x` — application: h1.comp x h2 ✓ standard form (comp takes x explicitly). The error: h2 \"has type HasDerivAt (fun x => x + ↑y * I) 1 ↑x but expected ?m.183 ?m.185 x\" — the `↑x` — h2's point is ↑x (cast) vs x — hasDerivAt_add_const_I y x : HasDerivAt (fun t => t + y * I) 1 x — x : ℝ ✓ — the display shows ↑x — the elaboration lifted x into ℂ?? — because in `h1.comp x h2`, comp expects hf : HasDerivAt f f' x with f : ? → ? and g at (f x): h1's point is (x + y * I) : ℂ — so f x = x + y*I needs x coerced to ℂ — Lean inferred f : ℂ → ℂ and x : ℂ, casting my x : ℝ to ↑x. But the inner parametrization is over ℝ! The HasDerivAt.comp for g : ℂ → ℂ and f : ℝ → ℂ — mixed-field composition is NOT HasDerivAt.comp (which needs same field!). PROBLEM: the chain rule for g ∘ f with f : ℝ → ℂ and g : ℂ → ℂ — the fields differ (ℝ for the real parameter, ℂ for g's holomorphic derivative). The composition's derivative is g'(f(x))·f'(x) as a complex number — the relevant lemma: `HasDerivAt.comp` requires g : 𝕜 → 𝕜 over the same 𝕜. For mixed: there's `HasDerivAt.comp_of_real`? or `HasDerivAt.comp'`? Hmm — actually for f : ℝ → ℂ differentiable (real derivative) and g : ℂ → ℂ holomorphic (complex derivative): the composition f(t) path in ℂ: (g∘f)'(t) = g'(f(t))·f'(t) — this is `HasDerivAt.comp` with 𝕜 = ... no. There should be a lemma for real-parameter curves into complex functions: `HasDerivAt.comp` doesn't apply; but there's `HasDerivAt.comp_hasDerivAt`? or use `HasFDerivAt.comp` with different scalars?? Hmm — actually the standard trick: g analytic ⟹ its real derivative along the path: use `HasDerivAt.comp` where BOTH are over ℝ? g's complex derivative gives the real derivative along any real-direction: HasDerivAt g (g' • (1 : ℂ)) — as a real-linear map: g is ℝ-differentiable with derivative (z ↦ g'·z): so the composition: HasFDerivAt-style. The cleanest Mathlib lemma: `HasDerivAt.comp` is for same-field. For mixed: `HasDerivAt.comp_ofReal`? Hmm. Alternative: `HasDerivAt.comp` exists in two flavors... Let me think about what the vendored PNT+ code does for parametrized sides — they must have faced this. Actually — the standard Mathlib lemma for this: `HasDerivAt.comp` with signature `(hg : HasDerivAt g (g') (f x)) (hf : HasDerivAt f (f') x) : HasDerivAt (g ∘ f) (g' * f') x` — fields: f : 𝕜 → F, g : F → F'... HasDerivAt is defined for functions between normed spaces over the SAME field 𝕜. For f : ℝ → ℂ and g : ℂ → ℂ: g is differentiable over ℂ; the composition over ℝ — the chain rule works with g's ℂ-derivative restricted to a real-linear map: the relevant instance: g is also ℝ-differentiable (DifferentiableAt ℂ g s → DifferentiableAt ℝ g s? — `DifferentiableAt.restrict_scalars`! There's `DifferentiableAt.restrict_scalars (h : DifferentiableAt ℂ f x) : DifferentiableAt ℝ f x` ✓ exists in Mathlib for restricted scalars. And then HasFDerivAt.comp for ℝ maps. The HasDerivAt (1-dimensional) version: `HasDerivAt.restrict_scalars`? Hmm.\n\nThis is getting heavy. Alternative cleaner approach for the side FTCs: AVOID the mixed-field chain rule by using `HasFDerivAt.comp` with CLMs? — or sidestep entirely: note that for our specific G (rational functions of (w−1)), the side integrands' antiderivatives are explicit — the FTC needs (x ↦ G(x+yI))' = G'(x+yI): prove it via `HasDerivAt.scomp`? Hmm.\n\nActually — the RIGHT Mathlib lemma: `HasDerivAt.comp` does exist in a version for f : 𝕜 → F, g : F → F' over the same field 𝕜... For f : ℝ → ℂ (𝕜 = ℝ, F = ℂ) and g : ℂ → ℂ (𝕜 = ℂ) — different fields. The composition's derivative over ℝ: need g ℝ-differentiable. `HasDerivAt.comp` in Mathlib is stated for g over the SAME 𝕜 as f. There's `HasDerivAt.comp` and `HasDerivAt.comp_hasDerivAt`... \n\nThe cleanest available: `HasFDerivAt.comp` (Fréchet, any normed spaces over the same field ℝ): G's HasFDerivAt (as a ℂ-differentiable function, restrict scalars to ℝ) with derivative the CLM (z ↦ G'·z); the path γ(x) = x + yI has HasFDerivAt with derivative (t ↦ t·1). Chain: (G∘γ)' = (z ↦ G'·z) ∘ (t ↦ t·1) = (t ↦ G'·t·1) = (t ↦ G'·t): so HasFDerivAt (G∘γ) (t ↦ G'·t) x — then to HasDerivAt: the 1-dim HasDerivAt from HasFDerivAt via `HasFDerivAt.hasDerivAt`? — for functions into ℂ over ℝ, HasDerivAt f f' x ⟺ HasFDerivAt f (f' • (1:ℝ→L[ℝ]ℂ))... there's `hasDerivAt_iff_hasFDerivAt`? \n\nSimplest robust hack: use `HasDerivAt.comp` with g viewed as a real function via restrict_scalars at the HasDerivAt level. Is there `HasDerivAt.restrict_scalars`? Let me grep. Actually — maybe easier: there IS a mixed composition lemma `HasDerivAt.comp` in Mathlib for this exact case? Let me grep for comp variants.","signature":""},{"type":"text","text":"The mixed-field chain rule needs the right lemma. Let me check what's available."},{"type":"tool_use","id":"Bash_228","name":"Bash","input":{"command":"cd /d/Python/Quantum/zeta-23-lean/.lake/packages/mathlib && grep -rn \"theorem HasDerivAt.restrict_scalars\\|lemma HasDerivAt.restrict_scalars\\|restrict_scalars.*HasDerivAt\" Mathlib/ --include=*.lean | head -4; grep -rn \"hasDerivAt_ofReal\\|ofRealCLM\" Mathlib/Analysis/Complex/Basic.lean | head -5; grep -rn \"theorem HasDerivAt.comp\\b\" Mathlib/Analysis/Calculus/Deriv/Comp.lean | head -3","description":"Find restrict_scalars and composition lemmas for mixed fields"},"extra_content":null}]