| Step | Hyp | Ref | Expression | 
						
							| 1 |  | lines.b |  |-  B = ( Base ` W ) | 
						
							| 2 |  | lines.l |  |-  L = ( LineM ` W ) | 
						
							| 3 |  | lines.s |  |-  S = ( Scalar ` W ) | 
						
							| 4 |  | lines.k |  |-  K = ( Base ` S ) | 
						
							| 5 |  | lines.p |  |-  .x. = ( .s ` W ) | 
						
							| 6 |  | lines.a |  |-  .+ = ( +g ` W ) | 
						
							| 7 |  | lines.m |  |-  .- = ( -g ` S ) | 
						
							| 8 |  | lines.1 |  |-  .1. = ( 1r ` S ) | 
						
							| 9 |  | df-line |  |-  LineM = ( w e. _V |-> ( x e. ( Base ` w ) , y e. ( ( Base ` w ) \ { x } ) |-> { p e. ( Base ` w ) | E. t e. ( Base ` ( Scalar ` w ) ) p = ( ( ( ( 1r ` ( Scalar ` w ) ) ( -g ` ( Scalar ` w ) ) t ) ( .s ` w ) x ) ( +g ` w ) ( t ( .s ` w ) y ) ) } ) ) | 
						
							| 10 |  | fveq2 |  |-  ( W = w -> ( Base ` W ) = ( Base ` w ) ) | 
						
							| 11 | 1 10 | eqtrid |  |-  ( W = w -> B = ( Base ` w ) ) | 
						
							| 12 | 11 | difeq1d |  |-  ( W = w -> ( B \ { x } ) = ( ( Base ` w ) \ { x } ) ) | 
						
							| 13 |  | fveq2 |  |-  ( W = w -> ( Scalar ` W ) = ( Scalar ` w ) ) | 
						
							| 14 | 3 13 | eqtrid |  |-  ( W = w -> S = ( Scalar ` w ) ) | 
						
							| 15 | 14 | fveq2d |  |-  ( W = w -> ( Base ` S ) = ( Base ` ( Scalar ` w ) ) ) | 
						
							| 16 | 4 15 | eqtrid |  |-  ( W = w -> K = ( Base ` ( Scalar ` w ) ) ) | 
						
							| 17 |  | fveq2 |  |-  ( W = w -> ( +g ` W ) = ( +g ` w ) ) | 
						
							| 18 | 6 17 | eqtrid |  |-  ( W = w -> .+ = ( +g ` w ) ) | 
						
							| 19 |  | fveq2 |  |-  ( W = w -> ( .s ` W ) = ( .s ` w ) ) | 
						
							| 20 | 5 19 | eqtrid |  |-  ( W = w -> .x. = ( .s ` w ) ) | 
						
							| 21 | 3 | fveq2i |  |-  ( -g ` S ) = ( -g ` ( Scalar ` W ) ) | 
						
							| 22 | 7 21 | eqtri |  |-  .- = ( -g ` ( Scalar ` W ) ) | 
						
							| 23 |  | 2fveq3 |  |-  ( W = w -> ( -g ` ( Scalar ` W ) ) = ( -g ` ( Scalar ` w ) ) ) | 
						
							| 24 | 22 23 | eqtrid |  |-  ( W = w -> .- = ( -g ` ( Scalar ` w ) ) ) | 
						
							| 25 | 3 | fveq2i |  |-  ( 1r ` S ) = ( 1r ` ( Scalar ` W ) ) | 
						
							| 26 | 8 25 | eqtri |  |-  .1. = ( 1r ` ( Scalar ` W ) ) | 
						
							| 27 |  | 2fveq3 |  |-  ( W = w -> ( 1r ` ( Scalar ` W ) ) = ( 1r ` ( Scalar ` w ) ) ) | 
						
							| 28 | 26 27 | eqtrid |  |-  ( W = w -> .1. = ( 1r ` ( Scalar ` w ) ) ) | 
						
							| 29 |  | eqidd |  |-  ( W = w -> t = t ) | 
						
							| 30 | 24 28 29 | oveq123d |  |-  ( W = w -> ( .1. .- t ) = ( ( 1r ` ( Scalar ` w ) ) ( -g ` ( Scalar ` w ) ) t ) ) | 
						
							| 31 |  | eqidd |  |-  ( W = w -> x = x ) | 
						
							| 32 | 20 30 31 | oveq123d |  |-  ( W = w -> ( ( .1. .- t ) .x. x ) = ( ( ( 1r ` ( Scalar ` w ) ) ( -g ` ( Scalar ` w ) ) t ) ( .s ` w ) x ) ) | 
						
							| 33 | 20 | oveqd |  |-  ( W = w -> ( t .x. y ) = ( t ( .s ` w ) y ) ) | 
						
							| 34 | 18 32 33 | oveq123d |  |-  ( W = w -> ( ( ( .1. .- t ) .x. x ) .+ ( t .x. y ) ) = ( ( ( ( 1r ` ( Scalar ` w ) ) ( -g ` ( Scalar ` w ) ) t ) ( .s ` w ) x ) ( +g ` w ) ( t ( .s ` w ) y ) ) ) | 
						
							| 35 | 34 | eqeq2d |  |-  ( W = w -> ( p = ( ( ( .1. .- t ) .x. x ) .+ ( t .x. y ) ) <-> p = ( ( ( ( 1r ` ( Scalar ` w ) ) ( -g ` ( Scalar ` w ) ) t ) ( .s ` w ) x ) ( +g ` w ) ( t ( .s ` w ) y ) ) ) ) | 
						
							| 36 | 16 35 | rexeqbidv |  |-  ( W = w -> ( E. t e. K p = ( ( ( .1. .- t ) .x. x ) .+ ( t .x. y ) ) <-> E. t e. ( Base ` ( Scalar ` w ) ) p = ( ( ( ( 1r ` ( Scalar ` w ) ) ( -g ` ( Scalar ` w ) ) t ) ( .s ` w ) x ) ( +g ` w ) ( t ( .s ` w ) y ) ) ) ) | 
						
							| 37 | 11 36 | rabeqbidv |  |-  ( W = w -> { p e. B | E. t e. K p = ( ( ( .1. .- t ) .x. x ) .+ ( t .x. y ) ) } = { p e. ( Base ` w ) | E. t e. ( Base ` ( Scalar ` w ) ) p = ( ( ( ( 1r ` ( Scalar ` w ) ) ( -g ` ( Scalar ` w ) ) t ) ( .s ` w ) x ) ( +g ` w ) ( t ( .s ` w ) y ) ) } ) | 
						
							| 38 | 11 12 37 | mpoeq123dv |  |-  ( W = w -> ( x e. B , y e. ( B \ { x } ) |-> { p e. B | E. t e. K p = ( ( ( .1. .- t ) .x. x ) .+ ( t .x. y ) ) } ) = ( x e. ( Base ` w ) , y e. ( ( Base ` w ) \ { x } ) |-> { p e. ( Base ` w ) | E. t e. ( Base ` ( Scalar ` w ) ) p = ( ( ( ( 1r ` ( Scalar ` w ) ) ( -g ` ( Scalar ` w ) ) t ) ( .s ` w ) x ) ( +g ` w ) ( t ( .s ` w ) y ) ) } ) ) | 
						
							| 39 | 38 | eqcomd |  |-  ( W = w -> ( x e. ( Base ` w ) , y e. ( ( Base ` w ) \ { x } ) |-> { p e. ( Base ` w ) | E. t e. ( Base ` ( Scalar ` w ) ) p = ( ( ( ( 1r ` ( Scalar ` w ) ) ( -g ` ( Scalar ` w ) ) t ) ( .s ` w ) x ) ( +g ` w ) ( t ( .s ` w ) y ) ) } ) = ( x e. B , y e. ( B \ { x } ) |-> { p e. B | E. t e. K p = ( ( ( .1. .- t ) .x. x ) .+ ( t .x. y ) ) } ) ) | 
						
							| 40 | 39 | eqcoms |  |-  ( w = W -> ( x e. ( Base ` w ) , y e. ( ( Base ` w ) \ { x } ) |-> { p e. ( Base ` w ) | E. t e. ( Base ` ( Scalar ` w ) ) p = ( ( ( ( 1r ` ( Scalar ` w ) ) ( -g ` ( Scalar ` w ) ) t ) ( .s ` w ) x ) ( +g ` w ) ( t ( .s ` w ) y ) ) } ) = ( x e. B , y e. ( B \ { x } ) |-> { p e. B | E. t e. K p = ( ( ( .1. .- t ) .x. x ) .+ ( t .x. y ) ) } ) ) | 
						
							| 41 |  | elex |  |-  ( W e. V -> W e. _V ) | 
						
							| 42 | 1 | fvexi |  |-  B e. _V | 
						
							| 43 | 42 | difexi |  |-  ( B \ { x } ) e. _V | 
						
							| 44 | 42 43 | mpoex |  |-  ( x e. B , y e. ( B \ { x } ) |-> { p e. B | E. t e. K p = ( ( ( .1. .- t ) .x. x ) .+ ( t .x. y ) ) } ) e. _V | 
						
							| 45 | 44 | a1i |  |-  ( W e. V -> ( x e. B , y e. ( B \ { x } ) |-> { p e. B | E. t e. K p = ( ( ( .1. .- t ) .x. x ) .+ ( t .x. y ) ) } ) e. _V ) | 
						
							| 46 | 9 40 41 45 | fvmptd3 |  |-  ( W e. V -> ( LineM ` W ) = ( x e. B , y e. ( B \ { x } ) |-> { p e. B | E. t e. K p = ( ( ( .1. .- t ) .x. x ) .+ ( t .x. y ) ) } ) ) | 
						
							| 47 | 2 46 | eqtrid |  |-  ( W e. V -> L = ( x e. B , y e. ( B \ { x } ) |-> { p e. B | E. t e. K p = ( ( ( .1. .- t ) .x. x ) .+ ( t .x. y ) ) } ) ) |