| Step | Hyp | Ref | Expression | 
						
							| 0 |  | csubmgm |  |-  SubMgm | 
						
							| 1 |  | vs |  |-  s | 
						
							| 2 |  | cmgm |  |-  Mgm | 
						
							| 3 |  | vt |  |-  t | 
						
							| 4 |  | cbs |  |-  Base | 
						
							| 5 | 1 | cv |  |-  s | 
						
							| 6 | 5 4 | cfv |  |-  ( Base ` s ) | 
						
							| 7 | 6 | cpw |  |-  ~P ( Base ` s ) | 
						
							| 8 |  | vx |  |-  x | 
						
							| 9 | 3 | cv |  |-  t | 
						
							| 10 |  | vy |  |-  y | 
						
							| 11 | 8 | cv |  |-  x | 
						
							| 12 |  | cplusg |  |-  +g | 
						
							| 13 | 5 12 | cfv |  |-  ( +g ` s ) | 
						
							| 14 | 10 | cv |  |-  y | 
						
							| 15 | 11 14 13 | co |  |-  ( x ( +g ` s ) y ) | 
						
							| 16 | 15 9 | wcel |  |-  ( x ( +g ` s ) y ) e. t | 
						
							| 17 | 16 10 9 | wral |  |-  A. y e. t ( x ( +g ` s ) y ) e. t | 
						
							| 18 | 17 8 9 | wral |  |-  A. x e. t A. y e. t ( x ( +g ` s ) y ) e. t | 
						
							| 19 | 18 3 7 | crab |  |-  { t e. ~P ( Base ` s ) | A. x e. t A. y e. t ( x ( +g ` s ) y ) e. t } | 
						
							| 20 | 1 2 19 | cmpt |  |-  ( s e. Mgm |-> { t e. ~P ( Base ` s ) | A. x e. t A. y e. t ( x ( +g ` s ) y ) e. t } ) | 
						
							| 21 | 0 20 | wceq |  |-  SubMgm = ( s e. Mgm |-> { t e. ~P ( Base ` s ) | A. x e. t A. y e. t ( x ( +g ` s ) y ) e. t } ) |