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Description: Express a word with an extra symbol as the union of the word and the new value. (Contributed by Mario Carneiro, 28-Feb-2016)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | cats1un | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( 𝐴 ++ 〈“ 𝐵 ”〉 ) = ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | ccatws1cl | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ∈ Word 𝑋 ) | |
| 2 | wrdf | ⊢ ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ∈ Word 𝑋 → ( 𝐴 ++ 〈“ 𝐵 ”〉 ) : ( 0 ..^ ( ♯ ‘ ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ) ) ⟶ 𝑋 ) | |
| 3 | 1 2 | syl | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( 𝐴 ++ 〈“ 𝐵 ”〉 ) : ( 0 ..^ ( ♯ ‘ ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ) ) ⟶ 𝑋 ) |
| 4 | ccatws1len | ⊢ ( 𝐴 ∈ Word 𝑋 → ( ♯ ‘ ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ) = ( ( ♯ ‘ 𝐴 ) + 1 ) ) | |
| 5 | 4 | oveq2d | ⊢ ( 𝐴 ∈ Word 𝑋 → ( 0 ..^ ( ♯ ‘ ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ) ) = ( 0 ..^ ( ( ♯ ‘ 𝐴 ) + 1 ) ) ) |
| 6 | lencl | ⊢ ( 𝐴 ∈ Word 𝑋 → ( ♯ ‘ 𝐴 ) ∈ ℕ0 ) | |
| 7 | nn0uz | ⊢ ℕ0 = ( ℤ≥ ‘ 0 ) | |
| 8 | 6 7 | eleqtrdi | ⊢ ( 𝐴 ∈ Word 𝑋 → ( ♯ ‘ 𝐴 ) ∈ ( ℤ≥ ‘ 0 ) ) |
| 9 | fzosplitsn | ⊢ ( ( ♯ ‘ 𝐴 ) ∈ ( ℤ≥ ‘ 0 ) → ( 0 ..^ ( ( ♯ ‘ 𝐴 ) + 1 ) ) = ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∪ { ( ♯ ‘ 𝐴 ) } ) ) | |
| 10 | 8 9 | syl | ⊢ ( 𝐴 ∈ Word 𝑋 → ( 0 ..^ ( ( ♯ ‘ 𝐴 ) + 1 ) ) = ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∪ { ( ♯ ‘ 𝐴 ) } ) ) |
| 11 | 5 10 | eqtrd | ⊢ ( 𝐴 ∈ Word 𝑋 → ( 0 ..^ ( ♯ ‘ ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ) ) = ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∪ { ( ♯ ‘ 𝐴 ) } ) ) |
| 12 | 11 | adantr | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( 0 ..^ ( ♯ ‘ ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ) ) = ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∪ { ( ♯ ‘ 𝐴 ) } ) ) |
| 13 | 12 | feq2d | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) : ( 0 ..^ ( ♯ ‘ ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ) ) ⟶ 𝑋 ↔ ( 𝐴 ++ 〈“ 𝐵 ”〉 ) : ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∪ { ( ♯ ‘ 𝐴 ) } ) ⟶ 𝑋 ) ) |
| 14 | 3 13 | mpbid | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( 𝐴 ++ 〈“ 𝐵 ”〉 ) : ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∪ { ( ♯ ‘ 𝐴 ) } ) ⟶ 𝑋 ) |
| 15 | 14 | ffnd | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( 𝐴 ++ 〈“ 𝐵 ”〉 ) Fn ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∪ { ( ♯ ‘ 𝐴 ) } ) ) |
| 16 | wrdf | ⊢ ( 𝐴 ∈ Word 𝑋 → 𝐴 : ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ⟶ 𝑋 ) | |
| 17 | 16 | adantr | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → 𝐴 : ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ⟶ 𝑋 ) |
| 18 | eqid | ⊢ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } = { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } | |
| 19 | fsng | ⊢ ( ( ( ♯ ‘ 𝐴 ) ∈ ℕ0 ∧ 𝐵 ∈ 𝑋 ) → ( { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } : { ( ♯ ‘ 𝐴 ) } ⟶ { 𝐵 } ↔ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } = { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ) | |
| 20 | 18 19 | mpbiri | ⊢ ( ( ( ♯ ‘ 𝐴 ) ∈ ℕ0 ∧ 𝐵 ∈ 𝑋 ) → { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } : { ( ♯ ‘ 𝐴 ) } ⟶ { 𝐵 } ) |
| 21 | 6 20 | sylan | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } : { ( ♯ ‘ 𝐴 ) } ⟶ { 𝐵 } ) |
| 22 | fzodisjsn | ⊢ ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∩ { ( ♯ ‘ 𝐴 ) } ) = ∅ | |
| 23 | 22 | a1i | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∩ { ( ♯ ‘ 𝐴 ) } ) = ∅ ) |
| 24 | fun | ⊢ ( ( ( 𝐴 : ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ⟶ 𝑋 ∧ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } : { ( ♯ ‘ 𝐴 ) } ⟶ { 𝐵 } ) ∧ ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∩ { ( ♯ ‘ 𝐴 ) } ) = ∅ ) → ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) : ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∪ { ( ♯ ‘ 𝐴 ) } ) ⟶ ( 𝑋 ∪ { 𝐵 } ) ) | |
| 25 | 17 21 23 24 | syl21anc | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) : ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∪ { ( ♯ ‘ 𝐴 ) } ) ⟶ ( 𝑋 ∪ { 𝐵 } ) ) |
| 26 | 25 | ffnd | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) Fn ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∪ { ( ♯ ‘ 𝐴 ) } ) ) |
| 27 | elun | ⊢ ( 𝑥 ∈ ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∪ { ( ♯ ‘ 𝐴 ) } ) ↔ ( 𝑥 ∈ ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∨ 𝑥 ∈ { ( ♯ ‘ 𝐴 ) } ) ) | |
| 28 | ccats1val1 | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝑥 ∈ ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ) → ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ 𝑥 ) = ( 𝐴 ‘ 𝑥 ) ) | |
| 29 | 28 | adantlr | ⊢ ( ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) ∧ 𝑥 ∈ ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ) → ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ 𝑥 ) = ( 𝐴 ‘ 𝑥 ) ) |
| 30 | simpr | ⊢ ( ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) ∧ 𝑥 ∈ ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ) → 𝑥 ∈ ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ) | |
| 31 | fzonel | ⊢ ¬ ( ♯ ‘ 𝐴 ) ∈ ( 0 ..^ ( ♯ ‘ 𝐴 ) ) | |
| 32 | nelne2 | ⊢ ( ( 𝑥 ∈ ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∧ ¬ ( ♯ ‘ 𝐴 ) ∈ ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ) → 𝑥 ≠ ( ♯ ‘ 𝐴 ) ) | |
| 33 | 30 31 32 | sylancl | ⊢ ( ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) ∧ 𝑥 ∈ ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ) → 𝑥 ≠ ( ♯ ‘ 𝐴 ) ) |
| 34 | 33 | necomd | ⊢ ( ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) ∧ 𝑥 ∈ ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ) → ( ♯ ‘ 𝐴 ) ≠ 𝑥 ) |
| 35 | fvunsn | ⊢ ( ( ♯ ‘ 𝐴 ) ≠ 𝑥 → ( ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ‘ 𝑥 ) = ( 𝐴 ‘ 𝑥 ) ) | |
| 36 | 34 35 | syl | ⊢ ( ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) ∧ 𝑥 ∈ ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ) → ( ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ‘ 𝑥 ) = ( 𝐴 ‘ 𝑥 ) ) |
| 37 | 29 36 | eqtr4d | ⊢ ( ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) ∧ 𝑥 ∈ ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ) → ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ 𝑥 ) = ( ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ‘ 𝑥 ) ) |
| 38 | fvexd | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( ♯ ‘ 𝐴 ) ∈ V ) | |
| 39 | simpr | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → 𝐵 ∈ 𝑋 ) | |
| 40 | 17 | fdmd | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → dom 𝐴 = ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ) |
| 41 | 40 | eleq2d | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( ( ♯ ‘ 𝐴 ) ∈ dom 𝐴 ↔ ( ♯ ‘ 𝐴 ) ∈ ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ) ) |
| 42 | 31 41 | mtbiri | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ¬ ( ♯ ‘ 𝐴 ) ∈ dom 𝐴 ) |
| 43 | fsnunfv | ⊢ ( ( ( ♯ ‘ 𝐴 ) ∈ V ∧ 𝐵 ∈ 𝑋 ∧ ¬ ( ♯ ‘ 𝐴 ) ∈ dom 𝐴 ) → ( ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ‘ ( ♯ ‘ 𝐴 ) ) = 𝐵 ) | |
| 44 | 38 39 42 43 | syl3anc | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ‘ ( ♯ ‘ 𝐴 ) ) = 𝐵 ) |
| 45 | simpl | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → 𝐴 ∈ Word 𝑋 ) | |
| 46 | s1cl | ⊢ ( 𝐵 ∈ 𝑋 → 〈“ 𝐵 ”〉 ∈ Word 𝑋 ) | |
| 47 | 46 | adantl | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → 〈“ 𝐵 ”〉 ∈ Word 𝑋 ) |
| 48 | s1len | ⊢ ( ♯ ‘ 〈“ 𝐵 ”〉 ) = 1 | |
| 49 | 1nn | ⊢ 1 ∈ ℕ | |
| 50 | 48 49 | eqeltri | ⊢ ( ♯ ‘ 〈“ 𝐵 ”〉 ) ∈ ℕ |
| 51 | lbfzo0 | ⊢ ( 0 ∈ ( 0 ..^ ( ♯ ‘ 〈“ 𝐵 ”〉 ) ) ↔ ( ♯ ‘ 〈“ 𝐵 ”〉 ) ∈ ℕ ) | |
| 52 | 50 51 | mpbir | ⊢ 0 ∈ ( 0 ..^ ( ♯ ‘ 〈“ 𝐵 ”〉 ) ) |
| 53 | 52 | a1i | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → 0 ∈ ( 0 ..^ ( ♯ ‘ 〈“ 𝐵 ”〉 ) ) ) |
| 54 | ccatval3 | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 〈“ 𝐵 ”〉 ∈ Word 𝑋 ∧ 0 ∈ ( 0 ..^ ( ♯ ‘ 〈“ 𝐵 ”〉 ) ) ) → ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ ( 0 + ( ♯ ‘ 𝐴 ) ) ) = ( 〈“ 𝐵 ”〉 ‘ 0 ) ) | |
| 55 | 45 47 53 54 | syl3anc | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ ( 0 + ( ♯ ‘ 𝐴 ) ) ) = ( 〈“ 𝐵 ”〉 ‘ 0 ) ) |
| 56 | s1fv | ⊢ ( 𝐵 ∈ 𝑋 → ( 〈“ 𝐵 ”〉 ‘ 0 ) = 𝐵 ) | |
| 57 | 56 | adantl | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( 〈“ 𝐵 ”〉 ‘ 0 ) = 𝐵 ) |
| 58 | 55 57 | eqtrd | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ ( 0 + ( ♯ ‘ 𝐴 ) ) ) = 𝐵 ) |
| 59 | 6 | adantr | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( ♯ ‘ 𝐴 ) ∈ ℕ0 ) |
| 60 | 59 | nn0cnd | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( ♯ ‘ 𝐴 ) ∈ ℂ ) |
| 61 | 60 | addlidd | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( 0 + ( ♯ ‘ 𝐴 ) ) = ( ♯ ‘ 𝐴 ) ) |
| 62 | 61 | fveq2d | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ ( 0 + ( ♯ ‘ 𝐴 ) ) ) = ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ ( ♯ ‘ 𝐴 ) ) ) |
| 63 | 44 58 62 | 3eqtr2rd | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ ( ♯ ‘ 𝐴 ) ) = ( ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ‘ ( ♯ ‘ 𝐴 ) ) ) |
| 64 | elsni | ⊢ ( 𝑥 ∈ { ( ♯ ‘ 𝐴 ) } → 𝑥 = ( ♯ ‘ 𝐴 ) ) | |
| 65 | 64 | fveq2d | ⊢ ( 𝑥 ∈ { ( ♯ ‘ 𝐴 ) } → ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ 𝑥 ) = ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ ( ♯ ‘ 𝐴 ) ) ) |
| 66 | 64 | fveq2d | ⊢ ( 𝑥 ∈ { ( ♯ ‘ 𝐴 ) } → ( ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ‘ 𝑥 ) = ( ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ‘ ( ♯ ‘ 𝐴 ) ) ) |
| 67 | 65 66 | eqeq12d | ⊢ ( 𝑥 ∈ { ( ♯ ‘ 𝐴 ) } → ( ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ 𝑥 ) = ( ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ‘ 𝑥 ) ↔ ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ ( ♯ ‘ 𝐴 ) ) = ( ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ‘ ( ♯ ‘ 𝐴 ) ) ) ) |
| 68 | 63 67 | syl5ibrcom | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( 𝑥 ∈ { ( ♯ ‘ 𝐴 ) } → ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ 𝑥 ) = ( ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ‘ 𝑥 ) ) ) |
| 69 | 68 | imp | ⊢ ( ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) ∧ 𝑥 ∈ { ( ♯ ‘ 𝐴 ) } ) → ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ 𝑥 ) = ( ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ‘ 𝑥 ) ) |
| 70 | 37 69 | jaodan | ⊢ ( ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) ∧ ( 𝑥 ∈ ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∨ 𝑥 ∈ { ( ♯ ‘ 𝐴 ) } ) ) → ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ 𝑥 ) = ( ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ‘ 𝑥 ) ) |
| 71 | 27 70 | sylan2b | ⊢ ( ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) ∧ 𝑥 ∈ ( ( 0 ..^ ( ♯ ‘ 𝐴 ) ) ∪ { ( ♯ ‘ 𝐴 ) } ) ) → ( ( 𝐴 ++ 〈“ 𝐵 ”〉 ) ‘ 𝑥 ) = ( ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ‘ 𝑥 ) ) |
| 72 | 15 26 71 | eqfnfvd | ⊢ ( ( 𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ 𝑋 ) → ( 𝐴 ++ 〈“ 𝐵 ”〉 ) = ( 𝐴 ∪ { 〈 ( ♯ ‘ 𝐴 ) , 𝐵 〉 } ) ) |