| Step | Hyp | Ref | Expression | 
						
							| 1 |  | srgmulgass.b | ⊢ 𝐵  =  ( Base ‘ 𝑅 ) | 
						
							| 2 |  | srgmulgass.m | ⊢  ·   =  ( .g ‘ 𝑅 ) | 
						
							| 3 |  | srgmulgass.t | ⊢  ×   =  ( .r ‘ 𝑅 ) | 
						
							| 4 |  | oveq1 | ⊢ ( 𝑥  =  0  →  ( 𝑥  ·  𝑋 )  =  ( 0  ·  𝑋 ) ) | 
						
							| 5 | 4 | oveq1d | ⊢ ( 𝑥  =  0  →  ( ( 𝑥  ·  𝑋 )  ×  𝑌 )  =  ( ( 0  ·  𝑋 )  ×  𝑌 ) ) | 
						
							| 6 |  | oveq1 | ⊢ ( 𝑥  =  0  →  ( 𝑥  ·  ( 𝑋  ×  𝑌 ) )  =  ( 0  ·  ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 7 | 5 6 | eqeq12d | ⊢ ( 𝑥  =  0  →  ( ( ( 𝑥  ·  𝑋 )  ×  𝑌 )  =  ( 𝑥  ·  ( 𝑋  ×  𝑌 ) )  ↔  ( ( 0  ·  𝑋 )  ×  𝑌 )  =  ( 0  ·  ( 𝑋  ×  𝑌 ) ) ) ) | 
						
							| 8 | 7 | imbi2d | ⊢ ( 𝑥  =  0  →  ( ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( 𝑥  ·  𝑋 )  ×  𝑌 )  =  ( 𝑥  ·  ( 𝑋  ×  𝑌 ) ) )  ↔  ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( 0  ·  𝑋 )  ×  𝑌 )  =  ( 0  ·  ( 𝑋  ×  𝑌 ) ) ) ) ) | 
						
							| 9 |  | oveq1 | ⊢ ( 𝑥  =  𝑦  →  ( 𝑥  ·  𝑋 )  =  ( 𝑦  ·  𝑋 ) ) | 
						
							| 10 | 9 | oveq1d | ⊢ ( 𝑥  =  𝑦  →  ( ( 𝑥  ·  𝑋 )  ×  𝑌 )  =  ( ( 𝑦  ·  𝑋 )  ×  𝑌 ) ) | 
						
							| 11 |  | oveq1 | ⊢ ( 𝑥  =  𝑦  →  ( 𝑥  ·  ( 𝑋  ×  𝑌 ) )  =  ( 𝑦  ·  ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 12 | 10 11 | eqeq12d | ⊢ ( 𝑥  =  𝑦  →  ( ( ( 𝑥  ·  𝑋 )  ×  𝑌 )  =  ( 𝑥  ·  ( 𝑋  ×  𝑌 ) )  ↔  ( ( 𝑦  ·  𝑋 )  ×  𝑌 )  =  ( 𝑦  ·  ( 𝑋  ×  𝑌 ) ) ) ) | 
						
							| 13 | 12 | imbi2d | ⊢ ( 𝑥  =  𝑦  →  ( ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( 𝑥  ·  𝑋 )  ×  𝑌 )  =  ( 𝑥  ·  ( 𝑋  ×  𝑌 ) ) )  ↔  ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( 𝑦  ·  𝑋 )  ×  𝑌 )  =  ( 𝑦  ·  ( 𝑋  ×  𝑌 ) ) ) ) ) | 
						
							| 14 |  | oveq1 | ⊢ ( 𝑥  =  ( 𝑦  +  1 )  →  ( 𝑥  ·  𝑋 )  =  ( ( 𝑦  +  1 )  ·  𝑋 ) ) | 
						
							| 15 | 14 | oveq1d | ⊢ ( 𝑥  =  ( 𝑦  +  1 )  →  ( ( 𝑥  ·  𝑋 )  ×  𝑌 )  =  ( ( ( 𝑦  +  1 )  ·  𝑋 )  ×  𝑌 ) ) | 
						
							| 16 |  | oveq1 | ⊢ ( 𝑥  =  ( 𝑦  +  1 )  →  ( 𝑥  ·  ( 𝑋  ×  𝑌 ) )  =  ( ( 𝑦  +  1 )  ·  ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 17 | 15 16 | eqeq12d | ⊢ ( 𝑥  =  ( 𝑦  +  1 )  →  ( ( ( 𝑥  ·  𝑋 )  ×  𝑌 )  =  ( 𝑥  ·  ( 𝑋  ×  𝑌 ) )  ↔  ( ( ( 𝑦  +  1 )  ·  𝑋 )  ×  𝑌 )  =  ( ( 𝑦  +  1 )  ·  ( 𝑋  ×  𝑌 ) ) ) ) | 
						
							| 18 | 17 | imbi2d | ⊢ ( 𝑥  =  ( 𝑦  +  1 )  →  ( ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( 𝑥  ·  𝑋 )  ×  𝑌 )  =  ( 𝑥  ·  ( 𝑋  ×  𝑌 ) ) )  ↔  ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( ( 𝑦  +  1 )  ·  𝑋 )  ×  𝑌 )  =  ( ( 𝑦  +  1 )  ·  ( 𝑋  ×  𝑌 ) ) ) ) ) | 
						
							| 19 |  | oveq1 | ⊢ ( 𝑥  =  𝑁  →  ( 𝑥  ·  𝑋 )  =  ( 𝑁  ·  𝑋 ) ) | 
						
							| 20 | 19 | oveq1d | ⊢ ( 𝑥  =  𝑁  →  ( ( 𝑥  ·  𝑋 )  ×  𝑌 )  =  ( ( 𝑁  ·  𝑋 )  ×  𝑌 ) ) | 
						
							| 21 |  | oveq1 | ⊢ ( 𝑥  =  𝑁  →  ( 𝑥  ·  ( 𝑋  ×  𝑌 ) )  =  ( 𝑁  ·  ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 22 | 20 21 | eqeq12d | ⊢ ( 𝑥  =  𝑁  →  ( ( ( 𝑥  ·  𝑋 )  ×  𝑌 )  =  ( 𝑥  ·  ( 𝑋  ×  𝑌 ) )  ↔  ( ( 𝑁  ·  𝑋 )  ×  𝑌 )  =  ( 𝑁  ·  ( 𝑋  ×  𝑌 ) ) ) ) | 
						
							| 23 | 22 | imbi2d | ⊢ ( 𝑥  =  𝑁  →  ( ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( 𝑥  ·  𝑋 )  ×  𝑌 )  =  ( 𝑥  ·  ( 𝑋  ×  𝑌 ) ) )  ↔  ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( 𝑁  ·  𝑋 )  ×  𝑌 )  =  ( 𝑁  ·  ( 𝑋  ×  𝑌 ) ) ) ) ) | 
						
							| 24 |  | simpr | ⊢ ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  𝑅  ∈  SRing ) | 
						
							| 25 |  | simpr | ⊢ ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  →  𝑌  ∈  𝐵 ) | 
						
							| 26 | 25 | adantr | ⊢ ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  𝑌  ∈  𝐵 ) | 
						
							| 27 |  | eqid | ⊢ ( 0g ‘ 𝑅 )  =  ( 0g ‘ 𝑅 ) | 
						
							| 28 | 1 3 27 | srglz | ⊢ ( ( 𝑅  ∈  SRing  ∧  𝑌  ∈  𝐵 )  →  ( ( 0g ‘ 𝑅 )  ×  𝑌 )  =  ( 0g ‘ 𝑅 ) ) | 
						
							| 29 | 24 26 28 | syl2anc | ⊢ ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( 0g ‘ 𝑅 )  ×  𝑌 )  =  ( 0g ‘ 𝑅 ) ) | 
						
							| 30 |  | simpl | ⊢ ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  →  𝑋  ∈  𝐵 ) | 
						
							| 31 | 30 | adantr | ⊢ ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  𝑋  ∈  𝐵 ) | 
						
							| 32 | 1 27 2 | mulg0 | ⊢ ( 𝑋  ∈  𝐵  →  ( 0  ·  𝑋 )  =  ( 0g ‘ 𝑅 ) ) | 
						
							| 33 | 31 32 | syl | ⊢ ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( 0  ·  𝑋 )  =  ( 0g ‘ 𝑅 ) ) | 
						
							| 34 | 33 | oveq1d | ⊢ ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( 0  ·  𝑋 )  ×  𝑌 )  =  ( ( 0g ‘ 𝑅 )  ×  𝑌 ) ) | 
						
							| 35 | 1 3 | srgcl | ⊢ ( ( 𝑅  ∈  SRing  ∧  𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  →  ( 𝑋  ×  𝑌 )  ∈  𝐵 ) | 
						
							| 36 | 24 31 26 35 | syl3anc | ⊢ ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( 𝑋  ×  𝑌 )  ∈  𝐵 ) | 
						
							| 37 | 1 27 2 | mulg0 | ⊢ ( ( 𝑋  ×  𝑌 )  ∈  𝐵  →  ( 0  ·  ( 𝑋  ×  𝑌 ) )  =  ( 0g ‘ 𝑅 ) ) | 
						
							| 38 | 36 37 | syl | ⊢ ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( 0  ·  ( 𝑋  ×  𝑌 ) )  =  ( 0g ‘ 𝑅 ) ) | 
						
							| 39 | 29 34 38 | 3eqtr4d | ⊢ ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( 0  ·  𝑋 )  ×  𝑌 )  =  ( 0  ·  ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 40 |  | srgmnd | ⊢ ( 𝑅  ∈  SRing  →  𝑅  ∈  Mnd ) | 
						
							| 41 | 40 | adantl | ⊢ ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  𝑅  ∈  Mnd ) | 
						
							| 42 | 41 | adantl | ⊢ ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  →  𝑅  ∈  Mnd ) | 
						
							| 43 |  | simpl | ⊢ ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  →  𝑦  ∈  ℕ0 ) | 
						
							| 44 | 31 | adantl | ⊢ ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  →  𝑋  ∈  𝐵 ) | 
						
							| 45 |  | eqid | ⊢ ( +g ‘ 𝑅 )  =  ( +g ‘ 𝑅 ) | 
						
							| 46 | 1 2 45 | mulgnn0p1 | ⊢ ( ( 𝑅  ∈  Mnd  ∧  𝑦  ∈  ℕ0  ∧  𝑋  ∈  𝐵 )  →  ( ( 𝑦  +  1 )  ·  𝑋 )  =  ( ( 𝑦  ·  𝑋 ) ( +g ‘ 𝑅 ) 𝑋 ) ) | 
						
							| 47 | 42 43 44 46 | syl3anc | ⊢ ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  →  ( ( 𝑦  +  1 )  ·  𝑋 )  =  ( ( 𝑦  ·  𝑋 ) ( +g ‘ 𝑅 ) 𝑋 ) ) | 
						
							| 48 | 47 | oveq1d | ⊢ ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  →  ( ( ( 𝑦  +  1 )  ·  𝑋 )  ×  𝑌 )  =  ( ( ( 𝑦  ·  𝑋 ) ( +g ‘ 𝑅 ) 𝑋 )  ×  𝑌 ) ) | 
						
							| 49 | 24 | adantl | ⊢ ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  →  𝑅  ∈  SRing ) | 
						
							| 50 | 1 2 42 43 44 | mulgnn0cld | ⊢ ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  →  ( 𝑦  ·  𝑋 )  ∈  𝐵 ) | 
						
							| 51 | 26 | adantl | ⊢ ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  →  𝑌  ∈  𝐵 ) | 
						
							| 52 | 1 45 3 | srgdir | ⊢ ( ( 𝑅  ∈  SRing  ∧  ( ( 𝑦  ·  𝑋 )  ∈  𝐵  ∧  𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 ) )  →  ( ( ( 𝑦  ·  𝑋 ) ( +g ‘ 𝑅 ) 𝑋 )  ×  𝑌 )  =  ( ( ( 𝑦  ·  𝑋 )  ×  𝑌 ) ( +g ‘ 𝑅 ) ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 53 | 49 50 44 51 52 | syl13anc | ⊢ ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  →  ( ( ( 𝑦  ·  𝑋 ) ( +g ‘ 𝑅 ) 𝑋 )  ×  𝑌 )  =  ( ( ( 𝑦  ·  𝑋 )  ×  𝑌 ) ( +g ‘ 𝑅 ) ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 54 | 48 53 | eqtrd | ⊢ ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  →  ( ( ( 𝑦  +  1 )  ·  𝑋 )  ×  𝑌 )  =  ( ( ( 𝑦  ·  𝑋 )  ×  𝑌 ) ( +g ‘ 𝑅 ) ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 55 | 54 | adantr | ⊢ ( ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  ∧  ( ( 𝑦  ·  𝑋 )  ×  𝑌 )  =  ( 𝑦  ·  ( 𝑋  ×  𝑌 ) ) )  →  ( ( ( 𝑦  +  1 )  ·  𝑋 )  ×  𝑌 )  =  ( ( ( 𝑦  ·  𝑋 )  ×  𝑌 ) ( +g ‘ 𝑅 ) ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 56 |  | oveq1 | ⊢ ( ( ( 𝑦  ·  𝑋 )  ×  𝑌 )  =  ( 𝑦  ·  ( 𝑋  ×  𝑌 ) )  →  ( ( ( 𝑦  ·  𝑋 )  ×  𝑌 ) ( +g ‘ 𝑅 ) ( 𝑋  ×  𝑌 ) )  =  ( ( 𝑦  ·  ( 𝑋  ×  𝑌 ) ) ( +g ‘ 𝑅 ) ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 57 | 35 | 3expb | ⊢ ( ( 𝑅  ∈  SRing  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 ) )  →  ( 𝑋  ×  𝑌 )  ∈  𝐵 ) | 
						
							| 58 | 57 | ancoms | ⊢ ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( 𝑋  ×  𝑌 )  ∈  𝐵 ) | 
						
							| 59 | 58 | adantl | ⊢ ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  →  ( 𝑋  ×  𝑌 )  ∈  𝐵 ) | 
						
							| 60 | 1 2 45 | mulgnn0p1 | ⊢ ( ( 𝑅  ∈  Mnd  ∧  𝑦  ∈  ℕ0  ∧  ( 𝑋  ×  𝑌 )  ∈  𝐵 )  →  ( ( 𝑦  +  1 )  ·  ( 𝑋  ×  𝑌 ) )  =  ( ( 𝑦  ·  ( 𝑋  ×  𝑌 ) ) ( +g ‘ 𝑅 ) ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 61 | 42 43 59 60 | syl3anc | ⊢ ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  →  ( ( 𝑦  +  1 )  ·  ( 𝑋  ×  𝑌 ) )  =  ( ( 𝑦  ·  ( 𝑋  ×  𝑌 ) ) ( +g ‘ 𝑅 ) ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 62 | 61 | eqcomd | ⊢ ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  →  ( ( 𝑦  ·  ( 𝑋  ×  𝑌 ) ) ( +g ‘ 𝑅 ) ( 𝑋  ×  𝑌 ) )  =  ( ( 𝑦  +  1 )  ·  ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 63 | 56 62 | sylan9eqr | ⊢ ( ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  ∧  ( ( 𝑦  ·  𝑋 )  ×  𝑌 )  =  ( 𝑦  ·  ( 𝑋  ×  𝑌 ) ) )  →  ( ( ( 𝑦  ·  𝑋 )  ×  𝑌 ) ( +g ‘ 𝑅 ) ( 𝑋  ×  𝑌 ) )  =  ( ( 𝑦  +  1 )  ·  ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 64 | 55 63 | eqtrd | ⊢ ( ( ( 𝑦  ∈  ℕ0  ∧  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing ) )  ∧  ( ( 𝑦  ·  𝑋 )  ×  𝑌 )  =  ( 𝑦  ·  ( 𝑋  ×  𝑌 ) ) )  →  ( ( ( 𝑦  +  1 )  ·  𝑋 )  ×  𝑌 )  =  ( ( 𝑦  +  1 )  ·  ( 𝑋  ×  𝑌 ) ) ) | 
						
							| 65 | 64 | exp31 | ⊢ ( 𝑦  ∈  ℕ0  →  ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( ( 𝑦  ·  𝑋 )  ×  𝑌 )  =  ( 𝑦  ·  ( 𝑋  ×  𝑌 ) )  →  ( ( ( 𝑦  +  1 )  ·  𝑋 )  ×  𝑌 )  =  ( ( 𝑦  +  1 )  ·  ( 𝑋  ×  𝑌 ) ) ) ) ) | 
						
							| 66 | 65 | a2d | ⊢ ( 𝑦  ∈  ℕ0  →  ( ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( 𝑦  ·  𝑋 )  ×  𝑌 )  =  ( 𝑦  ·  ( 𝑋  ×  𝑌 ) ) )  →  ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( ( 𝑦  +  1 )  ·  𝑋 )  ×  𝑌 )  =  ( ( 𝑦  +  1 )  ·  ( 𝑋  ×  𝑌 ) ) ) ) ) | 
						
							| 67 | 8 13 18 23 39 66 | nn0ind | ⊢ ( 𝑁  ∈  ℕ0  →  ( ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  ∧  𝑅  ∈  SRing )  →  ( ( 𝑁  ·  𝑋 )  ×  𝑌 )  =  ( 𝑁  ·  ( 𝑋  ×  𝑌 ) ) ) ) | 
						
							| 68 | 67 | expd | ⊢ ( 𝑁  ∈  ℕ0  →  ( ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  →  ( 𝑅  ∈  SRing  →  ( ( 𝑁  ·  𝑋 )  ×  𝑌 )  =  ( 𝑁  ·  ( 𝑋  ×  𝑌 ) ) ) ) ) | 
						
							| 69 | 68 | 3impib | ⊢ ( ( 𝑁  ∈  ℕ0  ∧  𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  →  ( 𝑅  ∈  SRing  →  ( ( 𝑁  ·  𝑋 )  ×  𝑌 )  =  ( 𝑁  ·  ( 𝑋  ×  𝑌 ) ) ) ) | 
						
							| 70 | 69 | impcom | ⊢ ( ( 𝑅  ∈  SRing  ∧  ( 𝑁  ∈  ℕ0  ∧  𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 ) )  →  ( ( 𝑁  ·  𝑋 )  ×  𝑌 )  =  ( 𝑁  ·  ( 𝑋  ×  𝑌 ) ) ) |