| Step | Hyp | Ref | Expression | 
						
							| 1 |  | mulgass.b |  |-  B = ( Base ` G ) | 
						
							| 2 |  | mulgass.t |  |-  .x. = ( .g ` G ) | 
						
							| 3 |  | mndsgrp |  |-  ( G e. Mnd -> G e. Smgrp ) | 
						
							| 4 | 3 | adantr |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> G e. Smgrp ) | 
						
							| 5 | 4 | adantr |  |-  ( ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) /\ ( M e. NN /\ N e. NN ) ) -> G e. Smgrp ) | 
						
							| 6 |  | simprl |  |-  ( ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) /\ ( M e. NN /\ N e. NN ) ) -> M e. NN ) | 
						
							| 7 |  | simprr |  |-  ( ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) /\ ( M e. NN /\ N e. NN ) ) -> N e. NN ) | 
						
							| 8 |  | simpr3 |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> X e. B ) | 
						
							| 9 | 8 | adantr |  |-  ( ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) /\ ( M e. NN /\ N e. NN ) ) -> X e. B ) | 
						
							| 10 | 1 2 | mulgnnass |  |-  ( ( G e. Smgrp /\ ( M e. NN /\ N e. NN /\ X e. B ) ) -> ( ( M x. N ) .x. X ) = ( M .x. ( N .x. X ) ) ) | 
						
							| 11 | 5 6 7 9 10 | syl13anc |  |-  ( ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) /\ ( M e. NN /\ N e. NN ) ) -> ( ( M x. N ) .x. X ) = ( M .x. ( N .x. X ) ) ) | 
						
							| 12 | 11 | expr |  |-  ( ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) /\ M e. NN ) -> ( N e. NN -> ( ( M x. N ) .x. X ) = ( M .x. ( N .x. X ) ) ) ) | 
						
							| 13 |  | eqid |  |-  ( 0g ` G ) = ( 0g ` G ) | 
						
							| 14 | 1 13 2 | mulg0 |  |-  ( X e. B -> ( 0 .x. X ) = ( 0g ` G ) ) | 
						
							| 15 | 8 14 | syl |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( 0 .x. X ) = ( 0g ` G ) ) | 
						
							| 16 |  | simpr1 |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> M e. NN0 ) | 
						
							| 17 | 16 | nn0cnd |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> M e. CC ) | 
						
							| 18 | 17 | mul01d |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( M x. 0 ) = 0 ) | 
						
							| 19 | 18 | oveq1d |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( ( M x. 0 ) .x. X ) = ( 0 .x. X ) ) | 
						
							| 20 | 15 | oveq2d |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( M .x. ( 0 .x. X ) ) = ( M .x. ( 0g ` G ) ) ) | 
						
							| 21 | 1 2 13 | mulgnn0z |  |-  ( ( G e. Mnd /\ M e. NN0 ) -> ( M .x. ( 0g ` G ) ) = ( 0g ` G ) ) | 
						
							| 22 | 21 | 3ad2antr1 |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( M .x. ( 0g ` G ) ) = ( 0g ` G ) ) | 
						
							| 23 | 20 22 | eqtrd |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( M .x. ( 0 .x. X ) ) = ( 0g ` G ) ) | 
						
							| 24 | 15 19 23 | 3eqtr4d |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( ( M x. 0 ) .x. X ) = ( M .x. ( 0 .x. X ) ) ) | 
						
							| 25 | 24 | adantr |  |-  ( ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) /\ M e. NN ) -> ( ( M x. 0 ) .x. X ) = ( M .x. ( 0 .x. X ) ) ) | 
						
							| 26 |  | oveq2 |  |-  ( N = 0 -> ( M x. N ) = ( M x. 0 ) ) | 
						
							| 27 | 26 | oveq1d |  |-  ( N = 0 -> ( ( M x. N ) .x. X ) = ( ( M x. 0 ) .x. X ) ) | 
						
							| 28 |  | oveq1 |  |-  ( N = 0 -> ( N .x. X ) = ( 0 .x. X ) ) | 
						
							| 29 | 28 | oveq2d |  |-  ( N = 0 -> ( M .x. ( N .x. X ) ) = ( M .x. ( 0 .x. X ) ) ) | 
						
							| 30 | 27 29 | eqeq12d |  |-  ( N = 0 -> ( ( ( M x. N ) .x. X ) = ( M .x. ( N .x. X ) ) <-> ( ( M x. 0 ) .x. X ) = ( M .x. ( 0 .x. X ) ) ) ) | 
						
							| 31 | 25 30 | syl5ibrcom |  |-  ( ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) /\ M e. NN ) -> ( N = 0 -> ( ( M x. N ) .x. X ) = ( M .x. ( N .x. X ) ) ) ) | 
						
							| 32 |  | simpr2 |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> N e. NN0 ) | 
						
							| 33 |  | elnn0 |  |-  ( N e. NN0 <-> ( N e. NN \/ N = 0 ) ) | 
						
							| 34 | 32 33 | sylib |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( N e. NN \/ N = 0 ) ) | 
						
							| 35 | 34 | adantr |  |-  ( ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) /\ M e. NN ) -> ( N e. NN \/ N = 0 ) ) | 
						
							| 36 | 12 31 35 | mpjaod |  |-  ( ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) /\ M e. NN ) -> ( ( M x. N ) .x. X ) = ( M .x. ( N .x. X ) ) ) | 
						
							| 37 | 36 | ex |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( M e. NN -> ( ( M x. N ) .x. X ) = ( M .x. ( N .x. X ) ) ) ) | 
						
							| 38 | 32 | nn0cnd |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> N e. CC ) | 
						
							| 39 | 38 | mul02d |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( 0 x. N ) = 0 ) | 
						
							| 40 | 39 | oveq1d |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( ( 0 x. N ) .x. X ) = ( 0 .x. X ) ) | 
						
							| 41 | 1 2 | mulgnn0cl |  |-  ( ( G e. Mnd /\ N e. NN0 /\ X e. B ) -> ( N .x. X ) e. B ) | 
						
							| 42 | 41 | 3adant3r1 |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( N .x. X ) e. B ) | 
						
							| 43 | 1 13 2 | mulg0 |  |-  ( ( N .x. X ) e. B -> ( 0 .x. ( N .x. X ) ) = ( 0g ` G ) ) | 
						
							| 44 | 42 43 | syl |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( 0 .x. ( N .x. X ) ) = ( 0g ` G ) ) | 
						
							| 45 | 15 40 44 | 3eqtr4d |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( ( 0 x. N ) .x. X ) = ( 0 .x. ( N .x. X ) ) ) | 
						
							| 46 |  | oveq1 |  |-  ( M = 0 -> ( M x. N ) = ( 0 x. N ) ) | 
						
							| 47 | 46 | oveq1d |  |-  ( M = 0 -> ( ( M x. N ) .x. X ) = ( ( 0 x. N ) .x. X ) ) | 
						
							| 48 |  | oveq1 |  |-  ( M = 0 -> ( M .x. ( N .x. X ) ) = ( 0 .x. ( N .x. X ) ) ) | 
						
							| 49 | 47 48 | eqeq12d |  |-  ( M = 0 -> ( ( ( M x. N ) .x. X ) = ( M .x. ( N .x. X ) ) <-> ( ( 0 x. N ) .x. X ) = ( 0 .x. ( N .x. X ) ) ) ) | 
						
							| 50 | 45 49 | syl5ibrcom |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( M = 0 -> ( ( M x. N ) .x. X ) = ( M .x. ( N .x. X ) ) ) ) | 
						
							| 51 |  | elnn0 |  |-  ( M e. NN0 <-> ( M e. NN \/ M = 0 ) ) | 
						
							| 52 | 16 51 | sylib |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( M e. NN \/ M = 0 ) ) | 
						
							| 53 | 37 50 52 | mpjaod |  |-  ( ( G e. Mnd /\ ( M e. NN0 /\ N e. NN0 /\ X e. B ) ) -> ( ( M x. N ) .x. X ) = ( M .x. ( N .x. X ) ) ) |