| Step | Hyp | Ref | Expression | 
						
							| 1 |  | osumcllem.l |  |-  .<_ = ( le ` K ) | 
						
							| 2 |  | osumcllem.j |  |-  .\/ = ( join ` K ) | 
						
							| 3 |  | osumcllem.a |  |-  A = ( Atoms ` K ) | 
						
							| 4 |  | osumcllem.p |  |-  .+ = ( +P ` K ) | 
						
							| 5 |  | osumcllem.o |  |-  ._|_ = ( _|_P ` K ) | 
						
							| 6 |  | osumcllem.c |  |-  C = ( PSubCl ` K ) | 
						
							| 7 |  | osumcllem.m |  |-  M = ( X .+ { p } ) | 
						
							| 8 |  | osumcllem.u |  |-  U = ( ._|_ ` ( ._|_ ` ( X .+ Y ) ) ) | 
						
							| 9 |  | simpl1 |  |-  ( ( ( K e. HL /\ X C_ A /\ Y C_ A ) /\ p e. U ) -> K e. HL ) | 
						
							| 10 |  | simpl2 |  |-  ( ( ( K e. HL /\ X C_ A /\ Y C_ A ) /\ p e. U ) -> X C_ A ) | 
						
							| 11 |  | simpr |  |-  ( ( ( K e. HL /\ X C_ A /\ Y C_ A ) /\ p e. U ) -> p e. U ) | 
						
							| 12 | 11 | snssd |  |-  ( ( ( K e. HL /\ X C_ A /\ Y C_ A ) /\ p e. U ) -> { p } C_ U ) | 
						
							| 13 | 3 4 | paddssat |  |-  ( ( K e. HL /\ X C_ A /\ Y C_ A ) -> ( X .+ Y ) C_ A ) | 
						
							| 14 | 13 | adantr |  |-  ( ( ( K e. HL /\ X C_ A /\ Y C_ A ) /\ p e. U ) -> ( X .+ Y ) C_ A ) | 
						
							| 15 | 3 5 | polssatN |  |-  ( ( K e. HL /\ ( X .+ Y ) C_ A ) -> ( ._|_ ` ( X .+ Y ) ) C_ A ) | 
						
							| 16 | 9 14 15 | syl2anc |  |-  ( ( ( K e. HL /\ X C_ A /\ Y C_ A ) /\ p e. U ) -> ( ._|_ ` ( X .+ Y ) ) C_ A ) | 
						
							| 17 | 3 5 | polssatN |  |-  ( ( K e. HL /\ ( ._|_ ` ( X .+ Y ) ) C_ A ) -> ( ._|_ ` ( ._|_ ` ( X .+ Y ) ) ) C_ A ) | 
						
							| 18 | 9 16 17 | syl2anc |  |-  ( ( ( K e. HL /\ X C_ A /\ Y C_ A ) /\ p e. U ) -> ( ._|_ ` ( ._|_ ` ( X .+ Y ) ) ) C_ A ) | 
						
							| 19 | 8 18 | eqsstrid |  |-  ( ( ( K e. HL /\ X C_ A /\ Y C_ A ) /\ p e. U ) -> U C_ A ) | 
						
							| 20 | 12 19 | sstrd |  |-  ( ( ( K e. HL /\ X C_ A /\ Y C_ A ) /\ p e. U ) -> { p } C_ A ) | 
						
							| 21 | 3 4 | sspadd1 |  |-  ( ( K e. HL /\ X C_ A /\ { p } C_ A ) -> X C_ ( X .+ { p } ) ) | 
						
							| 22 | 9 10 20 21 | syl3anc |  |-  ( ( ( K e. HL /\ X C_ A /\ Y C_ A ) /\ p e. U ) -> X C_ ( X .+ { p } ) ) | 
						
							| 23 | 22 7 | sseqtrrdi |  |-  ( ( ( K e. HL /\ X C_ A /\ Y C_ A ) /\ p e. U ) -> X C_ M ) | 
						
							| 24 | 1 2 3 4 5 6 7 8 | osumcllem1N |  |-  ( ( ( K e. HL /\ X C_ A /\ Y C_ A ) /\ p e. U ) -> ( U i^i M ) = M ) | 
						
							| 25 | 23 24 | sseqtrrd |  |-  ( ( ( K e. HL /\ X C_ A /\ Y C_ A ) /\ p e. U ) -> X C_ ( U i^i M ) ) |