| Step | Hyp | Ref | Expression | 
						
							| 1 |  | plyadd.1 | ⊢ ( 𝜑  →  𝐹  ∈  ( Poly ‘ 𝑆 ) ) | 
						
							| 2 |  | plyadd.2 | ⊢ ( 𝜑  →  𝐺  ∈  ( Poly ‘ 𝑆 ) ) | 
						
							| 3 |  | plyadd.3 | ⊢ ( ( 𝜑  ∧  ( 𝑥  ∈  𝑆  ∧  𝑦  ∈  𝑆 ) )  →  ( 𝑥  +  𝑦 )  ∈  𝑆 ) | 
						
							| 4 |  | plyadd.m | ⊢ ( 𝜑  →  𝑀  ∈  ℕ0 ) | 
						
							| 5 |  | plyadd.n | ⊢ ( 𝜑  →  𝑁  ∈  ℕ0 ) | 
						
							| 6 |  | plyadd.a | ⊢ ( 𝜑  →  𝐴  ∈  ( ( 𝑆  ∪  { 0 } )  ↑m  ℕ0 ) ) | 
						
							| 7 |  | plyadd.b | ⊢ ( 𝜑  →  𝐵  ∈  ( ( 𝑆  ∪  { 0 } )  ↑m  ℕ0 ) ) | 
						
							| 8 |  | plyadd.a2 | ⊢ ( 𝜑  →  ( 𝐴  “  ( ℤ≥ ‘ ( 𝑀  +  1 ) ) )  =  { 0 } ) | 
						
							| 9 |  | plyadd.b2 | ⊢ ( 𝜑  →  ( 𝐵  “  ( ℤ≥ ‘ ( 𝑁  +  1 ) ) )  =  { 0 } ) | 
						
							| 10 |  | plyadd.f | ⊢ ( 𝜑  →  𝐹  =  ( 𝑧  ∈  ℂ  ↦  Σ 𝑘  ∈  ( 0 ... 𝑀 ) ( ( 𝐴 ‘ 𝑘 )  ·  ( 𝑧 ↑ 𝑘 ) ) ) ) | 
						
							| 11 |  | plyadd.g | ⊢ ( 𝜑  →  𝐺  =  ( 𝑧  ∈  ℂ  ↦  Σ 𝑘  ∈  ( 0 ... 𝑁 ) ( ( 𝐵 ‘ 𝑘 )  ·  ( 𝑧 ↑ 𝑘 ) ) ) ) | 
						
							| 12 |  | plybss | ⊢ ( 𝐹  ∈  ( Poly ‘ 𝑆 )  →  𝑆  ⊆  ℂ ) | 
						
							| 13 | 1 12 | syl | ⊢ ( 𝜑  →  𝑆  ⊆  ℂ ) | 
						
							| 14 |  | 0cnd | ⊢ ( 𝜑  →  0  ∈  ℂ ) | 
						
							| 15 | 14 | snssd | ⊢ ( 𝜑  →  { 0 }  ⊆  ℂ ) | 
						
							| 16 | 13 15 | unssd | ⊢ ( 𝜑  →  ( 𝑆  ∪  { 0 } )  ⊆  ℂ ) | 
						
							| 17 |  | cnex | ⊢ ℂ  ∈  V | 
						
							| 18 |  | ssexg | ⊢ ( ( ( 𝑆  ∪  { 0 } )  ⊆  ℂ  ∧  ℂ  ∈  V )  →  ( 𝑆  ∪  { 0 } )  ∈  V ) | 
						
							| 19 | 16 17 18 | sylancl | ⊢ ( 𝜑  →  ( 𝑆  ∪  { 0 } )  ∈  V ) | 
						
							| 20 |  | nn0ex | ⊢ ℕ0  ∈  V | 
						
							| 21 |  | elmapg | ⊢ ( ( ( 𝑆  ∪  { 0 } )  ∈  V  ∧  ℕ0  ∈  V )  →  ( 𝐴  ∈  ( ( 𝑆  ∪  { 0 } )  ↑m  ℕ0 )  ↔  𝐴 : ℕ0 ⟶ ( 𝑆  ∪  { 0 } ) ) ) | 
						
							| 22 | 19 20 21 | sylancl | ⊢ ( 𝜑  →  ( 𝐴  ∈  ( ( 𝑆  ∪  { 0 } )  ↑m  ℕ0 )  ↔  𝐴 : ℕ0 ⟶ ( 𝑆  ∪  { 0 } ) ) ) | 
						
							| 23 | 6 22 | mpbid | ⊢ ( 𝜑  →  𝐴 : ℕ0 ⟶ ( 𝑆  ∪  { 0 } ) ) | 
						
							| 24 | 23 16 | fssd | ⊢ ( 𝜑  →  𝐴 : ℕ0 ⟶ ℂ ) | 
						
							| 25 |  | elmapg | ⊢ ( ( ( 𝑆  ∪  { 0 } )  ∈  V  ∧  ℕ0  ∈  V )  →  ( 𝐵  ∈  ( ( 𝑆  ∪  { 0 } )  ↑m  ℕ0 )  ↔  𝐵 : ℕ0 ⟶ ( 𝑆  ∪  { 0 } ) ) ) | 
						
							| 26 | 19 20 25 | sylancl | ⊢ ( 𝜑  →  ( 𝐵  ∈  ( ( 𝑆  ∪  { 0 } )  ↑m  ℕ0 )  ↔  𝐵 : ℕ0 ⟶ ( 𝑆  ∪  { 0 } ) ) ) | 
						
							| 27 | 7 26 | mpbid | ⊢ ( 𝜑  →  𝐵 : ℕ0 ⟶ ( 𝑆  ∪  { 0 } ) ) | 
						
							| 28 | 27 16 | fssd | ⊢ ( 𝜑  →  𝐵 : ℕ0 ⟶ ℂ ) | 
						
							| 29 | 1 2 4 5 24 28 8 9 10 11 | plyaddlem1 | ⊢ ( 𝜑  →  ( 𝐹  ∘f   +  𝐺 )  =  ( 𝑧  ∈  ℂ  ↦  Σ 𝑘  ∈  ( 0 ... if ( 𝑀  ≤  𝑁 ,  𝑁 ,  𝑀 ) ) ( ( ( 𝐴  ∘f   +  𝐵 ) ‘ 𝑘 )  ·  ( 𝑧 ↑ 𝑘 ) ) ) ) | 
						
							| 30 | 5 4 | ifcld | ⊢ ( 𝜑  →  if ( 𝑀  ≤  𝑁 ,  𝑁 ,  𝑀 )  ∈  ℕ0 ) | 
						
							| 31 |  | eqid | ⊢ ( 𝑆  ∪  { 0 } )  =  ( 𝑆  ∪  { 0 } ) | 
						
							| 32 | 13 31 3 | un0addcl | ⊢ ( ( 𝜑  ∧  ( 𝑥  ∈  ( 𝑆  ∪  { 0 } )  ∧  𝑦  ∈  ( 𝑆  ∪  { 0 } ) ) )  →  ( 𝑥  +  𝑦 )  ∈  ( 𝑆  ∪  { 0 } ) ) | 
						
							| 33 | 20 | a1i | ⊢ ( 𝜑  →  ℕ0  ∈  V ) | 
						
							| 34 |  | inidm | ⊢ ( ℕ0  ∩  ℕ0 )  =  ℕ0 | 
						
							| 35 | 32 23 27 33 33 34 | off | ⊢ ( 𝜑  →  ( 𝐴  ∘f   +  𝐵 ) : ℕ0 ⟶ ( 𝑆  ∪  { 0 } ) ) | 
						
							| 36 |  | elfznn0 | ⊢ ( 𝑘  ∈  ( 0 ... if ( 𝑀  ≤  𝑁 ,  𝑁 ,  𝑀 ) )  →  𝑘  ∈  ℕ0 ) | 
						
							| 37 |  | ffvelcdm | ⊢ ( ( ( 𝐴  ∘f   +  𝐵 ) : ℕ0 ⟶ ( 𝑆  ∪  { 0 } )  ∧  𝑘  ∈  ℕ0 )  →  ( ( 𝐴  ∘f   +  𝐵 ) ‘ 𝑘 )  ∈  ( 𝑆  ∪  { 0 } ) ) | 
						
							| 38 | 35 36 37 | syl2an | ⊢ ( ( 𝜑  ∧  𝑘  ∈  ( 0 ... if ( 𝑀  ≤  𝑁 ,  𝑁 ,  𝑀 ) ) )  →  ( ( 𝐴  ∘f   +  𝐵 ) ‘ 𝑘 )  ∈  ( 𝑆  ∪  { 0 } ) ) | 
						
							| 39 | 16 30 38 | elplyd | ⊢ ( 𝜑  →  ( 𝑧  ∈  ℂ  ↦  Σ 𝑘  ∈  ( 0 ... if ( 𝑀  ≤  𝑁 ,  𝑁 ,  𝑀 ) ) ( ( ( 𝐴  ∘f   +  𝐵 ) ‘ 𝑘 )  ·  ( 𝑧 ↑ 𝑘 ) ) )  ∈  ( Poly ‘ ( 𝑆  ∪  { 0 } ) ) ) | 
						
							| 40 | 29 39 | eqeltrd | ⊢ ( 𝜑  →  ( 𝐹  ∘f   +  𝐺 )  ∈  ( Poly ‘ ( 𝑆  ∪  { 0 } ) ) ) | 
						
							| 41 |  | plyun0 | ⊢ ( Poly ‘ ( 𝑆  ∪  { 0 } ) )  =  ( Poly ‘ 𝑆 ) | 
						
							| 42 | 40 41 | eleqtrdi | ⊢ ( 𝜑  →  ( 𝐹  ∘f   +  𝐺 )  ∈  ( Poly ‘ 𝑆 ) ) |