| Step | Hyp | Ref
 | Expression | 
| 1 |   | ofco.3 | 
. . . 4
⊢ (𝜑 → 𝐻:𝐷⟶𝐶) | 
| 2 | 1 | ffvelcdmda 5697 | 
. . 3
⊢ ((𝜑 ∧ 𝑥 ∈ 𝐷) → (𝐻‘𝑥) ∈ 𝐶) | 
| 3 | 1 | feqmptd 5614 | 
. . 3
⊢ (𝜑 → 𝐻 = (𝑥 ∈ 𝐷 ↦ (𝐻‘𝑥))) | 
| 4 |   | ofco.1 | 
. . . 4
⊢ (𝜑 → 𝐹 Fn 𝐴) | 
| 5 |   | ofco.2 | 
. . . 4
⊢ (𝜑 → 𝐺 Fn 𝐵) | 
| 6 |   | ofco.4 | 
. . . 4
⊢ (𝜑 → 𝐴 ∈ 𝑉) | 
| 7 |   | ofco.5 | 
. . . 4
⊢ (𝜑 → 𝐵 ∈ 𝑊) | 
| 8 |   | ofco.7 | 
. . . 4
⊢ (𝐴 ∩ 𝐵) = 𝐶 | 
| 9 |   | eqidd 2197 | 
. . . 4
⊢ ((𝜑 ∧ 𝑦 ∈ 𝐴) → (𝐹‘𝑦) = (𝐹‘𝑦)) | 
| 10 |   | eqidd 2197 | 
. . . 4
⊢ ((𝜑 ∧ 𝑦 ∈ 𝐵) → (𝐺‘𝑦) = (𝐺‘𝑦)) | 
| 11 | 4, 5, 6, 7, 8, 9, 10 | offval 6143 | 
. . 3
⊢ (𝜑 → (𝐹 ∘𝑓 𝑅𝐺) = (𝑦 ∈ 𝐶 ↦ ((𝐹‘𝑦)𝑅(𝐺‘𝑦)))) | 
| 12 |   | fveq2 5558 | 
. . . 4
⊢ (𝑦 = (𝐻‘𝑥) → (𝐹‘𝑦) = (𝐹‘(𝐻‘𝑥))) | 
| 13 |   | fveq2 5558 | 
. . . 4
⊢ (𝑦 = (𝐻‘𝑥) → (𝐺‘𝑦) = (𝐺‘(𝐻‘𝑥))) | 
| 14 | 12, 13 | oveq12d 5940 | 
. . 3
⊢ (𝑦 = (𝐻‘𝑥) → ((𝐹‘𝑦)𝑅(𝐺‘𝑦)) = ((𝐹‘(𝐻‘𝑥))𝑅(𝐺‘(𝐻‘𝑥)))) | 
| 15 | 2, 3, 11, 14 | fmptco 5728 | 
. 2
⊢ (𝜑 → ((𝐹 ∘𝑓 𝑅𝐺) ∘ 𝐻) = (𝑥 ∈ 𝐷 ↦ ((𝐹‘(𝐻‘𝑥))𝑅(𝐺‘(𝐻‘𝑥))))) | 
| 16 |   | inss1 3383 | 
. . . . . 6
⊢ (𝐴 ∩ 𝐵) ⊆ 𝐴 | 
| 17 | 8, 16 | eqsstrri 3216 | 
. . . . 5
⊢ 𝐶 ⊆ 𝐴 | 
| 18 |   | fss 5419 | 
. . . . 5
⊢ ((𝐻:𝐷⟶𝐶 ∧ 𝐶 ⊆ 𝐴) → 𝐻:𝐷⟶𝐴) | 
| 19 | 1, 17, 18 | sylancl 413 | 
. . . 4
⊢ (𝜑 → 𝐻:𝐷⟶𝐴) | 
| 20 |   | fnfco 5432 | 
. . . 4
⊢ ((𝐹 Fn 𝐴 ∧ 𝐻:𝐷⟶𝐴) → (𝐹 ∘ 𝐻) Fn 𝐷) | 
| 21 | 4, 19, 20 | syl2anc 411 | 
. . 3
⊢ (𝜑 → (𝐹 ∘ 𝐻) Fn 𝐷) | 
| 22 |   | inss2 3384 | 
. . . . . 6
⊢ (𝐴 ∩ 𝐵) ⊆ 𝐵 | 
| 23 | 8, 22 | eqsstrri 3216 | 
. . . . 5
⊢ 𝐶 ⊆ 𝐵 | 
| 24 |   | fss 5419 | 
. . . . 5
⊢ ((𝐻:𝐷⟶𝐶 ∧ 𝐶 ⊆ 𝐵) → 𝐻:𝐷⟶𝐵) | 
| 25 | 1, 23, 24 | sylancl 413 | 
. . . 4
⊢ (𝜑 → 𝐻:𝐷⟶𝐵) | 
| 26 |   | fnfco 5432 | 
. . . 4
⊢ ((𝐺 Fn 𝐵 ∧ 𝐻:𝐷⟶𝐵) → (𝐺 ∘ 𝐻) Fn 𝐷) | 
| 27 | 5, 25, 26 | syl2anc 411 | 
. . 3
⊢ (𝜑 → (𝐺 ∘ 𝐻) Fn 𝐷) | 
| 28 |   | ofco.6 | 
. . 3
⊢ (𝜑 → 𝐷 ∈ 𝑋) | 
| 29 |   | inidm 3372 | 
. . 3
⊢ (𝐷 ∩ 𝐷) = 𝐷 | 
| 30 |   | ffn 5407 | 
. . . . 5
⊢ (𝐻:𝐷⟶𝐶 → 𝐻 Fn 𝐷) | 
| 31 | 1, 30 | syl 14 | 
. . . 4
⊢ (𝜑 → 𝐻 Fn 𝐷) | 
| 32 |   | fvco2 5630 | 
. . . 4
⊢ ((𝐻 Fn 𝐷 ∧ 𝑥 ∈ 𝐷) → ((𝐹 ∘ 𝐻)‘𝑥) = (𝐹‘(𝐻‘𝑥))) | 
| 33 | 31, 32 | sylan 283 | 
. . 3
⊢ ((𝜑 ∧ 𝑥 ∈ 𝐷) → ((𝐹 ∘ 𝐻)‘𝑥) = (𝐹‘(𝐻‘𝑥))) | 
| 34 |   | fvco2 5630 | 
. . . 4
⊢ ((𝐻 Fn 𝐷 ∧ 𝑥 ∈ 𝐷) → ((𝐺 ∘ 𝐻)‘𝑥) = (𝐺‘(𝐻‘𝑥))) | 
| 35 | 31, 34 | sylan 283 | 
. . 3
⊢ ((𝜑 ∧ 𝑥 ∈ 𝐷) → ((𝐺 ∘ 𝐻)‘𝑥) = (𝐺‘(𝐻‘𝑥))) | 
| 36 | 21, 27, 28, 28, 29, 33, 35 | offval 6143 | 
. 2
⊢ (𝜑 → ((𝐹 ∘ 𝐻) ∘𝑓 𝑅(𝐺 ∘ 𝐻)) = (𝑥 ∈ 𝐷 ↦ ((𝐹‘(𝐻‘𝑥))𝑅(𝐺‘(𝐻‘𝑥))))) | 
| 37 | 15, 36 | eqtr4d 2232 | 
1
⊢ (𝜑 → ((𝐹 ∘𝑓 𝑅𝐺) ∘ 𝐻) = ((𝐹 ∘ 𝐻) ∘𝑓 𝑅(𝐺 ∘ 𝐻))) |