Metamath Proof Explorer


Theorem itcoval1

Description: A function iterated once. (Contributed by AV, 2-May-2024)

Ref Expression
Assertion itcoval1 ⊢ Rel ⁡ F ∧ F ∈ V → IterComp ⁡ F ⁡ 1 = F

Proof

Step Hyp Ref Expression
1 itcoval ⊢ F ∈ V → IterComp ⁡ F = seq 0 g ∈ V , j ∈ V ⟼ F ∘ g i ∈ ℕ 0 ⟼ if i = 0 I ↾ dom ⁡ F F
2 1 fveq1d ⊢ F ∈ V → IterComp ⁡ F ⁡ 1 = seq 0 g ∈ V , j ∈ V ⟼ F ∘ g i ∈ ℕ 0 ⟼ if i = 0 I ↾ dom ⁡ F F ⁡ 1
3 2 adantl ⊢ Rel ⁡ F ∧ F ∈ V → IterComp ⁡ F ⁡ 1 = seq 0 g ∈ V , j ∈ V ⟼ F ∘ g i ∈ ℕ 0 ⟼ if i = 0 I ↾ dom ⁡ F F ⁡ 1
4 nn0uz ⊢ ℕ 0 = ℤ ≥ 0
5 0nn0 ⊢ 0 ∈ ℕ 0
6 5 a1i ⊢ Rel ⁡ F ∧ F ∈ V → 0 ∈ ℕ 0
7 1e0p1 ⊢ 1 = 0 + 1
8 1 eqcomd ⊢ F ∈ V → seq 0 g ∈ V , j ∈ V ⟼ F ∘ g i ∈ ℕ 0 ⟼ if i = 0 I ↾ dom ⁡ F F = IterComp ⁡ F
9 8 fveq1d ⊢ F ∈ V → seq 0 g ∈ V , j ∈ V ⟼ F ∘ g i ∈ ℕ 0 ⟼ if i = 0 I ↾ dom ⁡ F F ⁡ 0 = IterComp ⁡ F ⁡ 0
10 itcoval0 ⊢ F ∈ V → IterComp ⁡ F ⁡ 0 = I ↾ dom ⁡ F
11 9 10 eqtrd ⊢ F ∈ V → seq 0 g ∈ V , j ∈ V ⟼ F ∘ g i ∈ ℕ 0 ⟼ if i = 0 I ↾ dom ⁡ F F ⁡ 0 = I ↾ dom ⁡ F
12 11 adantl ⊢ Rel ⁡ F ∧ F ∈ V → seq 0 g ∈ V , j ∈ V ⟼ F ∘ g i ∈ ℕ 0 ⟼ if i = 0 I ↾ dom ⁡ F F ⁡ 0 = I ↾ dom ⁡ F
13 eqidd ⊢ Rel ⁡ F ∧ F ∈ V → i ∈ ℕ 0 ⟼ if i = 0 I ↾ dom ⁡ F F = i ∈ ℕ 0 ⟼ if i = 0 I ↾ dom ⁡ F F
14 ax-1ne0 ⊢ 1 ≠ 0
15 14 neii ⊢ ¬ 1 = 0
16 eqeq1 ⊢ i = 1 → i = 0 ↔ 1 = 0
17 15 16 mtbiri ⊢ i = 1 → ¬ i = 0
18 17 iffalsed ⊢ i = 1 → if i = 0 I ↾ dom ⁡ F F = F
19 18 adantl ⊢ Rel ⁡ F ∧ F ∈ V ∧ i = 1 → if i = 0 I ↾ dom ⁡ F F = F
20 1nn0 ⊢ 1 ∈ ℕ 0
21 20 a1i ⊢ Rel ⁡ F ∧ F ∈ V → 1 ∈ ℕ 0
22 simpr ⊢ Rel ⁡ F ∧ F ∈ V → F ∈ V
23 13 19 21 22 fvmptd ⊢ Rel ⁡ F ∧ F ∈ V → i ∈ ℕ 0 ⟼ if i = 0 I ↾ dom ⁡ F F ⁡ 1 = F
24 4 6 7 12 23 seqp1d ⊢ Rel ⁡ F ∧ F ∈ V → seq 0 g ∈ V , j ∈ V ⟼ F ∘ g i ∈ ℕ 0 ⟼ if i = 0 I ↾ dom ⁡ F F ⁡ 1 = I ↾ dom ⁡ F g ∈ V , j ∈ V ⟼ F ∘ g F
25 eqidd ⊢ F ∈ V → g ∈ V , j ∈ V ⟼ F ∘ g = g ∈ V , j ∈ V ⟼ F ∘ g
26 coeq2 ⊢ g = I ↾ dom ⁡ F → F ∘ g = F ∘ I ↾ dom ⁡ F
27 26 ad2antrl ⊢ F ∈ V ∧ g = I ↾ dom ⁡ F ∧ j = F → F ∘ g = F ∘ I ↾ dom ⁡ F
28 dmexg ⊢ F ∈ V → dom ⁡ F ∈ V
29 28 resiexd ⊢ F ∈ V → I ↾ dom ⁡ F ∈ V
30 elex ⊢ F ∈ V → F ∈ V
31 coexg ⊢ F ∈ V ∧ I ↾ dom ⁡ F ∈ V → F ∘ I ↾ dom ⁡ F ∈ V
32 29 31 mpdan ⊢ F ∈ V → F ∘ I ↾ dom ⁡ F ∈ V
33 25 27 29 30 32 ovmpod ⊢ F ∈ V → I ↾ dom ⁡ F g ∈ V , j ∈ V ⟼ F ∘ g F = F ∘ I ↾ dom ⁡ F
34 33 adantl ⊢ Rel ⁡ F ∧ F ∈ V → I ↾ dom ⁡ F g ∈ V , j ∈ V ⟼ F ∘ g F = F ∘ I ↾ dom ⁡ F
35 coires1 ⊢ F ∘ I ↾ dom ⁡ F = F ↾ dom ⁡ F
36 resdm ⊢ Rel ⁡ F → F ↾ dom ⁡ F = F
37 36 adantr ⊢ Rel ⁡ F ∧ F ∈ V → F ↾ dom ⁡ F = F
38 35 37 eqtrid ⊢ Rel ⁡ F ∧ F ∈ V → F ∘ I ↾ dom ⁡ F = F
39 34 38 eqtrd ⊢ Rel ⁡ F ∧ F ∈ V → I ↾ dom ⁡ F g ∈ V , j ∈ V ⟼ F ∘ g F = F
40 24 39 eqtrd ⊢ Rel ⁡ F ∧ F ∈ V → seq 0 g ∈ V , j ∈ V ⟼ F ∘ g i ∈ ℕ 0 ⟼ if i = 0 I ↾ dom ⁡ F F ⁡ 1 = F
41 3 40 eqtrd ⊢ Rel ⁡ F ∧ F ∈ V → IterComp ⁡ F ⁡ 1 = F