-- Mathlib/Analysis/Analytic/Composition.lean
theorem applyComposition_update (p : FormalMultilinearSeries 𝕜 E F) {n : ℕ} (c : Composition n)
    (j : Fin n) (v : Fin n → E) (z : E) :
    p.applyComposition c (Function.update v j z) =
      Function.update (p.applyComposition c v) (c.index j)
        (p (c.blocksFun (c.index j))
          (Function.update (v ∘ c.embedding (c.index j)) (c.invEmbedding j) z))

Proof state:
case pos
𝕜 : Type u_1
E : Type u_2
F : Type u_3
inst✝¹⁰ : CommRing 𝕜
inst✝⁹ : AddCommGroup E
inst✝⁸ : AddCommGroup F
inst✝⁷ : Module 𝕜 E
inst✝⁶ : Module 𝕜 F
inst✝⁵ : TopologicalSpace E
inst✝⁴ : TopologicalSpace F
inst✝³ : IsTopologicalAddGroup E
inst✝² : ContinuousConstSMul 𝕜 E
inst✝¹ : IsTopologicalAddGroup F
inst✝ : ContinuousConstSMul 𝕜 F
p : FormalMultilinearSeries 𝕜 E F
n : ℕ
c : Composition n
j : Fin n
v : Fin n → E
z : E
k : Fin c.length
h : k = c.index j
r : Fin (c.blocksFun (c.index j)) → Fin n := ⇑(c.embedding (c.index j))
⊢ (p (c.blocksFun (c.index j))) (Function.update v j z ∘ r) =
    (p (c.blocksFun (c.index j))) (Function.update (v ∘ ⇑(c.embedding (c.index j))) (c.invEmbedding j) z)

Tactic:
let j' := c.invEmbedding j

Result:
case pos
𝕜 : Type u_1
E : Type u_2
F : Type u_3
inst✝¹⁰ : CommRing 𝕜
inst✝⁹ : AddCommGroup E
inst✝⁸ : AddCommGroup F
inst✝⁷ : Module 𝕜 E
inst✝⁶ : Module 𝕜 F
inst✝⁵ : TopologicalSpace E
inst✝⁴ : TopologicalSpace F
inst✝³ : IsTopologicalAddGroup E
inst✝² : ContinuousConstSMul 𝕜 E
inst✝¹ : IsTopologicalAddGroup F
inst✝ : ContinuousConstSMul 𝕜 F
p : FormalMultilinearSeries 𝕜 E F
n : ℕ
c : Composition n
j : Fin n
v : Fin n → E
z : E
k : Fin c.length
h : k = c.index j
r : Fin (c.blocksFun (c.index j)) → Fin n := ⇑(c.embedding (c.index j))
j' : Fin (c.blocksFun (c.index j)) := c.invEmbedding j
⊢ (p (c.blocksFun (c.index j))) (Function.update v j z ∘ r) =
    (p (c.blocksFun (c.index j))) (Function.update (v ∘ ⇑(c.embedding (c.index j))) (c.invEmbedding j) z)

Proof state:
case pos
𝕜 : Type u_1
E : Type u_2
F : Type u_3
inst✝¹⁰ : CommRing 𝕜
inst✝⁹ : AddCommGroup E
inst✝⁸ : AddCommGroup F
inst✝⁷ : Module 𝕜 E
inst✝⁶ : Module 𝕜 F
inst✝⁵ : TopologicalSpace E
inst✝⁴ : TopologicalSpace F
inst✝³ : IsTopologicalAddGroup E
inst✝² : ContinuousConstSMul 𝕜 E
inst✝¹ : IsTopologicalAddGroup F
inst✝ : ContinuousConstSMul 𝕜 F
p : FormalMultilinearSeries 𝕜 E F
n : ℕ
c : Composition n
j : Fin n
v : Fin n → E
z : E
k : Fin c.length
h : k = c.index j
r : Fin (c.blocksFun (c.index j)) → Fin n := ⇑(c.embedding (c.index j))
j' : Fin (c.blocksFun (c.index j)) := c.invEmbedding j
⊢ Function.update v (r j') z ∘ r = Function.update (v ∘ r) j' z

Tactic:
exact Function.update_comp_eq_of_injective _ (c.embedding _).injective _ _

Result:
no goals

Proof state:
case pos
𝕜 : Type u_1
E : Type u_2
F : Type u_3
inst✝¹⁰ : CommRing 𝕜
inst✝⁹ : AddCommGroup E
inst✝⁸ : AddCommGroup F
inst✝⁷ : Module 𝕜 E
inst✝⁶ : Module 𝕜 F
inst✝⁵ : TopologicalSpace E
inst✝⁴ : TopologicalSpace F
inst✝³ : IsTopologicalAddGroup E
inst✝² : ContinuousConstSMul 𝕜 E
inst✝¹ : IsTopologicalAddGroup F
inst✝ : ContinuousConstSMul 𝕜 F
p : FormalMultilinearSeries 𝕜 E F
n : ℕ
c : Composition n
j : Fin n
v : Fin n → E
z : E
k : Fin c.length
h : k = c.index j
r : Fin (c.blocksFun (c.index j)) → Fin n := ⇑(c.embedding (c.index j))
⊢ p.applyComposition c (Function.update v j z) (c.index j) =
    Function.update (p.applyComposition c v) (c.index j)
      ((p (c.blocksFun (c.index j))) (Function.update (v ∘ ⇑(c.embedding (c.index j))) (c.invEmbedding j) z))
      (c.index j)

Tactic:
simp only [Function.update_self]

Result:
case pos
𝕜 : Type u_1
E : Type u_2
F : Type u_3
inst✝¹⁰ : CommRing 𝕜
inst✝⁹ : AddCommGroup E
inst✝⁸ : AddCommGroup F
inst✝⁷ : Module 𝕜 E
inst✝⁶ : Module 𝕜 F
inst✝⁵ : TopologicalSpace E
inst✝⁴ : TopologicalSpace F
inst✝³ : IsTopologicalAddGroup E
inst✝² : ContinuousConstSMul 𝕜 E
inst✝¹ : IsTopologicalAddGroup F
inst✝ : ContinuousConstSMul 𝕜 F
p : FormalMultilinearSeries 𝕜 E F
n : ℕ
c : Composition n
j : Fin n
v : Fin n → E
z : E
k : Fin c.length
h : k = c.index j
r : Fin (c.blocksFun (c.index j)) → Fin n := ⇑(c.embedding (c.index j))
⊢ p.applyComposition c (Function.update v j z) (c.index j) =
    (p (c.blocksFun (c.index j))) (Function.update (v ∘ ⇑(c.embedding (c.index j))) (c.invEmbedding j) z)

Proof state:
𝕜 : Type u_1
E : Type u_2
F : Type u_3
inst✝¹⁰ : CommRing 𝕜
inst✝⁹ : AddCommGroup E
inst✝⁸ : AddCommGroup F
inst✝⁷ : Module 𝕜 E
inst✝⁶ : Module 𝕜 F
inst✝⁵ : TopologicalSpace E
inst✝⁴ : TopologicalSpace F
inst✝³ : IsTopologicalAddGroup E
inst✝² : ContinuousConstSMul 𝕜 E
inst✝¹ : IsTopologicalAddGroup F
inst✝ : ContinuousConstSMul 𝕜 F
p : FormalMultilinearSeries 𝕜 E F
n : ℕ
c : Composition n
j : Fin n
v : Fin n → E
z : E
k : Fin c.length
h : ¬k = c.index j
r : Fin (c.blocksFun k) → Fin n := ⇑(c.embedding k)
B : Function.update v j z ∘ r = v ∘ r
⊢ (p (c.blocksFun k)) (Function.update v j z ∘ r) = (p (c.blocksFun k)) (v ∘ r)

Tactic:
rw [B]

Result:
no goals