| Step | Hyp | Ref | Expression | 
						
							| 1 |  | hashxplem.1 | ⊢ 𝐵  ∈  Fin | 
						
							| 2 |  | xpeq1 | ⊢ ( 𝑥  =  ∅  →  ( 𝑥  ×  𝐵 )  =  ( ∅  ×  𝐵 ) ) | 
						
							| 3 | 2 | fveq2d | ⊢ ( 𝑥  =  ∅  →  ( ♯ ‘ ( 𝑥  ×  𝐵 ) )  =  ( ♯ ‘ ( ∅  ×  𝐵 ) ) ) | 
						
							| 4 |  | fveq2 | ⊢ ( 𝑥  =  ∅  →  ( ♯ ‘ 𝑥 )  =  ( ♯ ‘ ∅ ) ) | 
						
							| 5 | 4 | oveq1d | ⊢ ( 𝑥  =  ∅  →  ( ( ♯ ‘ 𝑥 )  ·  ( ♯ ‘ 𝐵 ) )  =  ( ( ♯ ‘ ∅ )  ·  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 6 | 3 5 | eqeq12d | ⊢ ( 𝑥  =  ∅  →  ( ( ♯ ‘ ( 𝑥  ×  𝐵 ) )  =  ( ( ♯ ‘ 𝑥 )  ·  ( ♯ ‘ 𝐵 ) )  ↔  ( ♯ ‘ ( ∅  ×  𝐵 ) )  =  ( ( ♯ ‘ ∅ )  ·  ( ♯ ‘ 𝐵 ) ) ) ) | 
						
							| 7 |  | xpeq1 | ⊢ ( 𝑥  =  𝑦  →  ( 𝑥  ×  𝐵 )  =  ( 𝑦  ×  𝐵 ) ) | 
						
							| 8 | 7 | fveq2d | ⊢ ( 𝑥  =  𝑦  →  ( ♯ ‘ ( 𝑥  ×  𝐵 ) )  =  ( ♯ ‘ ( 𝑦  ×  𝐵 ) ) ) | 
						
							| 9 |  | fveq2 | ⊢ ( 𝑥  =  𝑦  →  ( ♯ ‘ 𝑥 )  =  ( ♯ ‘ 𝑦 ) ) | 
						
							| 10 | 9 | oveq1d | ⊢ ( 𝑥  =  𝑦  →  ( ( ♯ ‘ 𝑥 )  ·  ( ♯ ‘ 𝐵 ) )  =  ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 11 | 8 10 | eqeq12d | ⊢ ( 𝑥  =  𝑦  →  ( ( ♯ ‘ ( 𝑥  ×  𝐵 ) )  =  ( ( ♯ ‘ 𝑥 )  ·  ( ♯ ‘ 𝐵 ) )  ↔  ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  =  ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) ) ) ) | 
						
							| 12 |  | xpeq1 | ⊢ ( 𝑥  =  ( 𝑦  ∪  { 𝑧 } )  →  ( 𝑥  ×  𝐵 )  =  ( ( 𝑦  ∪  { 𝑧 } )  ×  𝐵 ) ) | 
						
							| 13 | 12 | fveq2d | ⊢ ( 𝑥  =  ( 𝑦  ∪  { 𝑧 } )  →  ( ♯ ‘ ( 𝑥  ×  𝐵 ) )  =  ( ♯ ‘ ( ( 𝑦  ∪  { 𝑧 } )  ×  𝐵 ) ) ) | 
						
							| 14 |  | fveq2 | ⊢ ( 𝑥  =  ( 𝑦  ∪  { 𝑧 } )  →  ( ♯ ‘ 𝑥 )  =  ( ♯ ‘ ( 𝑦  ∪  { 𝑧 } ) ) ) | 
						
							| 15 | 14 | oveq1d | ⊢ ( 𝑥  =  ( 𝑦  ∪  { 𝑧 } )  →  ( ( ♯ ‘ 𝑥 )  ·  ( ♯ ‘ 𝐵 ) )  =  ( ( ♯ ‘ ( 𝑦  ∪  { 𝑧 } ) )  ·  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 16 | 13 15 | eqeq12d | ⊢ ( 𝑥  =  ( 𝑦  ∪  { 𝑧 } )  →  ( ( ♯ ‘ ( 𝑥  ×  𝐵 ) )  =  ( ( ♯ ‘ 𝑥 )  ·  ( ♯ ‘ 𝐵 ) )  ↔  ( ♯ ‘ ( ( 𝑦  ∪  { 𝑧 } )  ×  𝐵 ) )  =  ( ( ♯ ‘ ( 𝑦  ∪  { 𝑧 } ) )  ·  ( ♯ ‘ 𝐵 ) ) ) ) | 
						
							| 17 |  | xpeq1 | ⊢ ( 𝑥  =  𝐴  →  ( 𝑥  ×  𝐵 )  =  ( 𝐴  ×  𝐵 ) ) | 
						
							| 18 | 17 | fveq2d | ⊢ ( 𝑥  =  𝐴  →  ( ♯ ‘ ( 𝑥  ×  𝐵 ) )  =  ( ♯ ‘ ( 𝐴  ×  𝐵 ) ) ) | 
						
							| 19 |  | fveq2 | ⊢ ( 𝑥  =  𝐴  →  ( ♯ ‘ 𝑥 )  =  ( ♯ ‘ 𝐴 ) ) | 
						
							| 20 | 19 | oveq1d | ⊢ ( 𝑥  =  𝐴  →  ( ( ♯ ‘ 𝑥 )  ·  ( ♯ ‘ 𝐵 ) )  =  ( ( ♯ ‘ 𝐴 )  ·  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 21 | 18 20 | eqeq12d | ⊢ ( 𝑥  =  𝐴  →  ( ( ♯ ‘ ( 𝑥  ×  𝐵 ) )  =  ( ( ♯ ‘ 𝑥 )  ·  ( ♯ ‘ 𝐵 ) )  ↔  ( ♯ ‘ ( 𝐴  ×  𝐵 ) )  =  ( ( ♯ ‘ 𝐴 )  ·  ( ♯ ‘ 𝐵 ) ) ) ) | 
						
							| 22 |  | hashcl | ⊢ ( 𝐵  ∈  Fin  →  ( ♯ ‘ 𝐵 )  ∈  ℕ0 ) | 
						
							| 23 | 22 | nn0cnd | ⊢ ( 𝐵  ∈  Fin  →  ( ♯ ‘ 𝐵 )  ∈  ℂ ) | 
						
							| 24 | 23 | mul02d | ⊢ ( 𝐵  ∈  Fin  →  ( 0  ·  ( ♯ ‘ 𝐵 ) )  =  0 ) | 
						
							| 25 | 1 24 | ax-mp | ⊢ ( 0  ·  ( ♯ ‘ 𝐵 ) )  =  0 | 
						
							| 26 |  | hash0 | ⊢ ( ♯ ‘ ∅ )  =  0 | 
						
							| 27 | 26 | oveq1i | ⊢ ( ( ♯ ‘ ∅ )  ·  ( ♯ ‘ 𝐵 ) )  =  ( 0  ·  ( ♯ ‘ 𝐵 ) ) | 
						
							| 28 |  | 0xp | ⊢ ( ∅  ×  𝐵 )  =  ∅ | 
						
							| 29 | 28 | fveq2i | ⊢ ( ♯ ‘ ( ∅  ×  𝐵 ) )  =  ( ♯ ‘ ∅ ) | 
						
							| 30 | 29 26 | eqtri | ⊢ ( ♯ ‘ ( ∅  ×  𝐵 ) )  =  0 | 
						
							| 31 | 25 27 30 | 3eqtr4ri | ⊢ ( ♯ ‘ ( ∅  ×  𝐵 ) )  =  ( ( ♯ ‘ ∅ )  ·  ( ♯ ‘ 𝐵 ) ) | 
						
							| 32 |  | oveq1 | ⊢ ( ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  =  ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) )  →  ( ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  +  ( ♯ ‘ 𝐵 ) )  =  ( ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) )  +  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 33 | 32 | adantl | ⊢ ( ( ( 𝑦  ∈  Fin  ∧  ¬  𝑧  ∈  𝑦 )  ∧  ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  =  ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) ) )  →  ( ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  +  ( ♯ ‘ 𝐵 ) )  =  ( ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) )  +  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 34 |  | xpundir | ⊢ ( ( 𝑦  ∪  { 𝑧 } )  ×  𝐵 )  =  ( ( 𝑦  ×  𝐵 )  ∪  ( { 𝑧 }  ×  𝐵 ) ) | 
						
							| 35 | 34 | fveq2i | ⊢ ( ♯ ‘ ( ( 𝑦  ∪  { 𝑧 } )  ×  𝐵 ) )  =  ( ♯ ‘ ( ( 𝑦  ×  𝐵 )  ∪  ( { 𝑧 }  ×  𝐵 ) ) ) | 
						
							| 36 |  | xpfi | ⊢ ( ( 𝑦  ∈  Fin  ∧  𝐵  ∈  Fin )  →  ( 𝑦  ×  𝐵 )  ∈  Fin ) | 
						
							| 37 | 1 36 | mpan2 | ⊢ ( 𝑦  ∈  Fin  →  ( 𝑦  ×  𝐵 )  ∈  Fin ) | 
						
							| 38 |  | inxp | ⊢ ( ( 𝑦  ×  𝐵 )  ∩  ( { 𝑧 }  ×  𝐵 ) )  =  ( ( 𝑦  ∩  { 𝑧 } )  ×  ( 𝐵  ∩  𝐵 ) ) | 
						
							| 39 |  | disjsn | ⊢ ( ( 𝑦  ∩  { 𝑧 } )  =  ∅  ↔  ¬  𝑧  ∈  𝑦 ) | 
						
							| 40 | 39 | biimpri | ⊢ ( ¬  𝑧  ∈  𝑦  →  ( 𝑦  ∩  { 𝑧 } )  =  ∅ ) | 
						
							| 41 | 40 | xpeq1d | ⊢ ( ¬  𝑧  ∈  𝑦  →  ( ( 𝑦  ∩  { 𝑧 } )  ×  ( 𝐵  ∩  𝐵 ) )  =  ( ∅  ×  ( 𝐵  ∩  𝐵 ) ) ) | 
						
							| 42 |  | 0xp | ⊢ ( ∅  ×  ( 𝐵  ∩  𝐵 ) )  =  ∅ | 
						
							| 43 | 41 42 | eqtrdi | ⊢ ( ¬  𝑧  ∈  𝑦  →  ( ( 𝑦  ∩  { 𝑧 } )  ×  ( 𝐵  ∩  𝐵 ) )  =  ∅ ) | 
						
							| 44 | 38 43 | eqtrid | ⊢ ( ¬  𝑧  ∈  𝑦  →  ( ( 𝑦  ×  𝐵 )  ∩  ( { 𝑧 }  ×  𝐵 ) )  =  ∅ ) | 
						
							| 45 |  | snfi | ⊢ { 𝑧 }  ∈  Fin | 
						
							| 46 |  | xpfi | ⊢ ( ( { 𝑧 }  ∈  Fin  ∧  𝐵  ∈  Fin )  →  ( { 𝑧 }  ×  𝐵 )  ∈  Fin ) | 
						
							| 47 | 45 1 46 | mp2an | ⊢ ( { 𝑧 }  ×  𝐵 )  ∈  Fin | 
						
							| 48 |  | hashun | ⊢ ( ( ( 𝑦  ×  𝐵 )  ∈  Fin  ∧  ( { 𝑧 }  ×  𝐵 )  ∈  Fin  ∧  ( ( 𝑦  ×  𝐵 )  ∩  ( { 𝑧 }  ×  𝐵 ) )  =  ∅ )  →  ( ♯ ‘ ( ( 𝑦  ×  𝐵 )  ∪  ( { 𝑧 }  ×  𝐵 ) ) )  =  ( ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  +  ( ♯ ‘ ( { 𝑧 }  ×  𝐵 ) ) ) ) | 
						
							| 49 | 47 48 | mp3an2 | ⊢ ( ( ( 𝑦  ×  𝐵 )  ∈  Fin  ∧  ( ( 𝑦  ×  𝐵 )  ∩  ( { 𝑧 }  ×  𝐵 ) )  =  ∅ )  →  ( ♯ ‘ ( ( 𝑦  ×  𝐵 )  ∪  ( { 𝑧 }  ×  𝐵 ) ) )  =  ( ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  +  ( ♯ ‘ ( { 𝑧 }  ×  𝐵 ) ) ) ) | 
						
							| 50 | 37 44 49 | syl2an | ⊢ ( ( 𝑦  ∈  Fin  ∧  ¬  𝑧  ∈  𝑦 )  →  ( ♯ ‘ ( ( 𝑦  ×  𝐵 )  ∪  ( { 𝑧 }  ×  𝐵 ) ) )  =  ( ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  +  ( ♯ ‘ ( { 𝑧 }  ×  𝐵 ) ) ) ) | 
						
							| 51 |  | snex | ⊢ { 𝑧 }  ∈  V | 
						
							| 52 | 1 | elexi | ⊢ 𝐵  ∈  V | 
						
							| 53 | 51 52 | xpcomen | ⊢ ( { 𝑧 }  ×  𝐵 )  ≈  ( 𝐵  ×  { 𝑧 } ) | 
						
							| 54 |  | vex | ⊢ 𝑧  ∈  V | 
						
							| 55 | 52 54 | xpsnen | ⊢ ( 𝐵  ×  { 𝑧 } )  ≈  𝐵 | 
						
							| 56 | 53 55 | entri | ⊢ ( { 𝑧 }  ×  𝐵 )  ≈  𝐵 | 
						
							| 57 |  | hashen | ⊢ ( ( ( { 𝑧 }  ×  𝐵 )  ∈  Fin  ∧  𝐵  ∈  Fin )  →  ( ( ♯ ‘ ( { 𝑧 }  ×  𝐵 ) )  =  ( ♯ ‘ 𝐵 )  ↔  ( { 𝑧 }  ×  𝐵 )  ≈  𝐵 ) ) | 
						
							| 58 | 47 1 57 | mp2an | ⊢ ( ( ♯ ‘ ( { 𝑧 }  ×  𝐵 ) )  =  ( ♯ ‘ 𝐵 )  ↔  ( { 𝑧 }  ×  𝐵 )  ≈  𝐵 ) | 
						
							| 59 | 56 58 | mpbir | ⊢ ( ♯ ‘ ( { 𝑧 }  ×  𝐵 ) )  =  ( ♯ ‘ 𝐵 ) | 
						
							| 60 | 59 | oveq2i | ⊢ ( ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  +  ( ♯ ‘ ( { 𝑧 }  ×  𝐵 ) ) )  =  ( ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  +  ( ♯ ‘ 𝐵 ) ) | 
						
							| 61 | 50 60 | eqtrdi | ⊢ ( ( 𝑦  ∈  Fin  ∧  ¬  𝑧  ∈  𝑦 )  →  ( ♯ ‘ ( ( 𝑦  ×  𝐵 )  ∪  ( { 𝑧 }  ×  𝐵 ) ) )  =  ( ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  +  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 62 | 35 61 | eqtrid | ⊢ ( ( 𝑦  ∈  Fin  ∧  ¬  𝑧  ∈  𝑦 )  →  ( ♯ ‘ ( ( 𝑦  ∪  { 𝑧 } )  ×  𝐵 ) )  =  ( ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  +  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 63 | 62 | adantr | ⊢ ( ( ( 𝑦  ∈  Fin  ∧  ¬  𝑧  ∈  𝑦 )  ∧  ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  =  ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) ) )  →  ( ♯ ‘ ( ( 𝑦  ∪  { 𝑧 } )  ×  𝐵 ) )  =  ( ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  +  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 64 |  | hashunsng | ⊢ ( 𝑧  ∈  V  →  ( ( 𝑦  ∈  Fin  ∧  ¬  𝑧  ∈  𝑦 )  →  ( ♯ ‘ ( 𝑦  ∪  { 𝑧 } ) )  =  ( ( ♯ ‘ 𝑦 )  +  1 ) ) ) | 
						
							| 65 | 54 64 | ax-mp | ⊢ ( ( 𝑦  ∈  Fin  ∧  ¬  𝑧  ∈  𝑦 )  →  ( ♯ ‘ ( 𝑦  ∪  { 𝑧 } ) )  =  ( ( ♯ ‘ 𝑦 )  +  1 ) ) | 
						
							| 66 | 65 | oveq1d | ⊢ ( ( 𝑦  ∈  Fin  ∧  ¬  𝑧  ∈  𝑦 )  →  ( ( ♯ ‘ ( 𝑦  ∪  { 𝑧 } ) )  ·  ( ♯ ‘ 𝐵 ) )  =  ( ( ( ♯ ‘ 𝑦 )  +  1 )  ·  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 67 |  | hashcl | ⊢ ( 𝑦  ∈  Fin  →  ( ♯ ‘ 𝑦 )  ∈  ℕ0 ) | 
						
							| 68 | 67 | nn0cnd | ⊢ ( 𝑦  ∈  Fin  →  ( ♯ ‘ 𝑦 )  ∈  ℂ ) | 
						
							| 69 |  | ax-1cn | ⊢ 1  ∈  ℂ | 
						
							| 70 |  | nn0cn | ⊢ ( ( ♯ ‘ 𝐵 )  ∈  ℕ0  →  ( ♯ ‘ 𝐵 )  ∈  ℂ ) | 
						
							| 71 | 1 22 70 | mp2b | ⊢ ( ♯ ‘ 𝐵 )  ∈  ℂ | 
						
							| 72 |  | adddir | ⊢ ( ( ( ♯ ‘ 𝑦 )  ∈  ℂ  ∧  1  ∈  ℂ  ∧  ( ♯ ‘ 𝐵 )  ∈  ℂ )  →  ( ( ( ♯ ‘ 𝑦 )  +  1 )  ·  ( ♯ ‘ 𝐵 ) )  =  ( ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) )  +  ( 1  ·  ( ♯ ‘ 𝐵 ) ) ) ) | 
						
							| 73 | 69 71 72 | mp3an23 | ⊢ ( ( ♯ ‘ 𝑦 )  ∈  ℂ  →  ( ( ( ♯ ‘ 𝑦 )  +  1 )  ·  ( ♯ ‘ 𝐵 ) )  =  ( ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) )  +  ( 1  ·  ( ♯ ‘ 𝐵 ) ) ) ) | 
						
							| 74 | 68 73 | syl | ⊢ ( 𝑦  ∈  Fin  →  ( ( ( ♯ ‘ 𝑦 )  +  1 )  ·  ( ♯ ‘ 𝐵 ) )  =  ( ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) )  +  ( 1  ·  ( ♯ ‘ 𝐵 ) ) ) ) | 
						
							| 75 | 71 | mullidi | ⊢ ( 1  ·  ( ♯ ‘ 𝐵 ) )  =  ( ♯ ‘ 𝐵 ) | 
						
							| 76 | 75 | oveq2i | ⊢ ( ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) )  +  ( 1  ·  ( ♯ ‘ 𝐵 ) ) )  =  ( ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) )  +  ( ♯ ‘ 𝐵 ) ) | 
						
							| 77 | 74 76 | eqtrdi | ⊢ ( 𝑦  ∈  Fin  →  ( ( ( ♯ ‘ 𝑦 )  +  1 )  ·  ( ♯ ‘ 𝐵 ) )  =  ( ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) )  +  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 78 | 77 | adantr | ⊢ ( ( 𝑦  ∈  Fin  ∧  ¬  𝑧  ∈  𝑦 )  →  ( ( ( ♯ ‘ 𝑦 )  +  1 )  ·  ( ♯ ‘ 𝐵 ) )  =  ( ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) )  +  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 79 | 66 78 | eqtrd | ⊢ ( ( 𝑦  ∈  Fin  ∧  ¬  𝑧  ∈  𝑦 )  →  ( ( ♯ ‘ ( 𝑦  ∪  { 𝑧 } ) )  ·  ( ♯ ‘ 𝐵 ) )  =  ( ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) )  +  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 80 | 79 | adantr | ⊢ ( ( ( 𝑦  ∈  Fin  ∧  ¬  𝑧  ∈  𝑦 )  ∧  ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  =  ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) ) )  →  ( ( ♯ ‘ ( 𝑦  ∪  { 𝑧 } ) )  ·  ( ♯ ‘ 𝐵 ) )  =  ( ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) )  +  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 81 | 33 63 80 | 3eqtr4d | ⊢ ( ( ( 𝑦  ∈  Fin  ∧  ¬  𝑧  ∈  𝑦 )  ∧  ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  =  ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) ) )  →  ( ♯ ‘ ( ( 𝑦  ∪  { 𝑧 } )  ×  𝐵 ) )  =  ( ( ♯ ‘ ( 𝑦  ∪  { 𝑧 } ) )  ·  ( ♯ ‘ 𝐵 ) ) ) | 
						
							| 82 | 81 | ex | ⊢ ( ( 𝑦  ∈  Fin  ∧  ¬  𝑧  ∈  𝑦 )  →  ( ( ♯ ‘ ( 𝑦  ×  𝐵 ) )  =  ( ( ♯ ‘ 𝑦 )  ·  ( ♯ ‘ 𝐵 ) )  →  ( ♯ ‘ ( ( 𝑦  ∪  { 𝑧 } )  ×  𝐵 ) )  =  ( ( ♯ ‘ ( 𝑦  ∪  { 𝑧 } ) )  ·  ( ♯ ‘ 𝐵 ) ) ) ) | 
						
							| 83 | 6 11 16 21 31 82 | findcard2s | ⊢ ( 𝐴  ∈  Fin  →  ( ♯ ‘ ( 𝐴  ×  𝐵 ) )  =  ( ( ♯ ‘ 𝐴 )  ·  ( ♯ ‘ 𝐵 ) ) ) |