| Step | Hyp | Ref | Expression | 
						
							| 1 |  | iwrdsplit.s |  |-  ( ph -> S e. _V ) | 
						
							| 2 |  | iwrdsplit.f |  |-  ( ph -> F : NN0 --> S ) | 
						
							| 3 |  | iwrdsplit.n |  |-  ( ph -> N e. NN0 ) | 
						
							| 4 |  | 1nn0 |  |-  1 e. NN0 | 
						
							| 5 | 4 | a1i |  |-  ( ph -> 1 e. NN0 ) | 
						
							| 6 | 3 5 | nn0addcld |  |-  ( ph -> ( N + 1 ) e. NN0 ) | 
						
							| 7 | 1 2 6 | subiwrd |  |-  ( ph -> ( F |` ( 0 ..^ ( N + 1 ) ) ) e. Word S ) | 
						
							| 8 |  | 1re |  |-  1 e. RR | 
						
							| 9 |  | nn0addge2 |  |-  ( ( 1 e. RR /\ N e. NN0 ) -> 1 <_ ( N + 1 ) ) | 
						
							| 10 | 8 3 9 | sylancr |  |-  ( ph -> 1 <_ ( N + 1 ) ) | 
						
							| 11 | 1 2 6 | subiwrdlen |  |-  ( ph -> ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) = ( N + 1 ) ) | 
						
							| 12 | 10 11 | breqtrrd |  |-  ( ph -> 1 <_ ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) ) | 
						
							| 13 |  | wrdlenge1n0 |  |-  ( ( F |` ( 0 ..^ ( N + 1 ) ) ) e. Word S -> ( ( F |` ( 0 ..^ ( N + 1 ) ) ) =/= (/) <-> 1 <_ ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) ) ) | 
						
							| 14 | 7 13 | syl |  |-  ( ph -> ( ( F |` ( 0 ..^ ( N + 1 ) ) ) =/= (/) <-> 1 <_ ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) ) ) | 
						
							| 15 | 12 14 | mpbird |  |-  ( ph -> ( F |` ( 0 ..^ ( N + 1 ) ) ) =/= (/) ) | 
						
							| 16 |  | pfxlswccat |  |-  ( ( ( F |` ( 0 ..^ ( N + 1 ) ) ) e. Word S /\ ( F |` ( 0 ..^ ( N + 1 ) ) ) =/= (/) ) -> ( ( ( F |` ( 0 ..^ ( N + 1 ) ) ) prefix ( ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) - 1 ) ) ++ <" ( lastS ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) "> ) = ( F |` ( 0 ..^ ( N + 1 ) ) ) ) | 
						
							| 17 | 7 15 16 | syl2anc |  |-  ( ph -> ( ( ( F |` ( 0 ..^ ( N + 1 ) ) ) prefix ( ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) - 1 ) ) ++ <" ( lastS ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) "> ) = ( F |` ( 0 ..^ ( N + 1 ) ) ) ) | 
						
							| 18 | 3 | nn0cnd |  |-  ( ph -> N e. CC ) | 
						
							| 19 |  | 1cnd |  |-  ( ph -> 1 e. CC ) | 
						
							| 20 | 18 19 11 | mvrraddd |  |-  ( ph -> ( ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) - 1 ) = N ) | 
						
							| 21 | 20 | oveq2d |  |-  ( ph -> ( ( F |` ( 0 ..^ ( N + 1 ) ) ) prefix ( ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) - 1 ) ) = ( ( F |` ( 0 ..^ ( N + 1 ) ) ) prefix N ) ) | 
						
							| 22 |  | nn0fz0 |  |-  ( N e. NN0 <-> N e. ( 0 ... N ) ) | 
						
							| 23 | 3 22 | sylib |  |-  ( ph -> N e. ( 0 ... N ) ) | 
						
							| 24 |  | elfz0add |  |-  ( ( N e. NN0 /\ 1 e. NN0 ) -> ( N e. ( 0 ... N ) -> N e. ( 0 ... ( N + 1 ) ) ) ) | 
						
							| 25 | 24 | imp |  |-  ( ( ( N e. NN0 /\ 1 e. NN0 ) /\ N e. ( 0 ... N ) ) -> N e. ( 0 ... ( N + 1 ) ) ) | 
						
							| 26 | 3 5 23 25 | syl21anc |  |-  ( ph -> N e. ( 0 ... ( N + 1 ) ) ) | 
						
							| 27 | 11 | oveq2d |  |-  ( ph -> ( 0 ... ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) ) = ( 0 ... ( N + 1 ) ) ) | 
						
							| 28 | 26 27 | eleqtrrd |  |-  ( ph -> N e. ( 0 ... ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) ) ) | 
						
							| 29 |  | pfxres |  |-  ( ( ( F |` ( 0 ..^ ( N + 1 ) ) ) e. Word S /\ N e. ( 0 ... ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) ) ) -> ( ( F |` ( 0 ..^ ( N + 1 ) ) ) prefix N ) = ( ( F |` ( 0 ..^ ( N + 1 ) ) ) |` ( 0 ..^ N ) ) ) | 
						
							| 30 | 7 28 29 | syl2anc |  |-  ( ph -> ( ( F |` ( 0 ..^ ( N + 1 ) ) ) prefix N ) = ( ( F |` ( 0 ..^ ( N + 1 ) ) ) |` ( 0 ..^ N ) ) ) | 
						
							| 31 |  | fzossfzop1 |  |-  ( N e. NN0 -> ( 0 ..^ N ) C_ ( 0 ..^ ( N + 1 ) ) ) | 
						
							| 32 |  | resabs1 |  |-  ( ( 0 ..^ N ) C_ ( 0 ..^ ( N + 1 ) ) -> ( ( F |` ( 0 ..^ ( N + 1 ) ) ) |` ( 0 ..^ N ) ) = ( F |` ( 0 ..^ N ) ) ) | 
						
							| 33 | 3 31 32 | 3syl |  |-  ( ph -> ( ( F |` ( 0 ..^ ( N + 1 ) ) ) |` ( 0 ..^ N ) ) = ( F |` ( 0 ..^ N ) ) ) | 
						
							| 34 | 21 30 33 | 3eqtrd |  |-  ( ph -> ( ( F |` ( 0 ..^ ( N + 1 ) ) ) prefix ( ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) - 1 ) ) = ( F |` ( 0 ..^ N ) ) ) | 
						
							| 35 |  | lsw |  |-  ( ( F |` ( 0 ..^ ( N + 1 ) ) ) e. Word S -> ( lastS ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) = ( ( F |` ( 0 ..^ ( N + 1 ) ) ) ` ( ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) - 1 ) ) ) | 
						
							| 36 | 7 35 | syl |  |-  ( ph -> ( lastS ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) = ( ( F |` ( 0 ..^ ( N + 1 ) ) ) ` ( ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) - 1 ) ) ) | 
						
							| 37 | 20 | fveq2d |  |-  ( ph -> ( ( F |` ( 0 ..^ ( N + 1 ) ) ) ` ( ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) - 1 ) ) = ( ( F |` ( 0 ..^ ( N + 1 ) ) ) ` N ) ) | 
						
							| 38 |  | fzonn0p1 |  |-  ( N e. NN0 -> N e. ( 0 ..^ ( N + 1 ) ) ) | 
						
							| 39 |  | fvres |  |-  ( N e. ( 0 ..^ ( N + 1 ) ) -> ( ( F |` ( 0 ..^ ( N + 1 ) ) ) ` N ) = ( F ` N ) ) | 
						
							| 40 | 3 38 39 | 3syl |  |-  ( ph -> ( ( F |` ( 0 ..^ ( N + 1 ) ) ) ` N ) = ( F ` N ) ) | 
						
							| 41 | 36 37 40 | 3eqtrd |  |-  ( ph -> ( lastS ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) = ( F ` N ) ) | 
						
							| 42 | 41 | s1eqd |  |-  ( ph -> <" ( lastS ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) "> = <" ( F ` N ) "> ) | 
						
							| 43 | 34 42 | oveq12d |  |-  ( ph -> ( ( ( F |` ( 0 ..^ ( N + 1 ) ) ) prefix ( ( # ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) - 1 ) ) ++ <" ( lastS ` ( F |` ( 0 ..^ ( N + 1 ) ) ) ) "> ) = ( ( F |` ( 0 ..^ N ) ) ++ <" ( F ` N ) "> ) ) | 
						
							| 44 | 17 43 | eqtr3d |  |-  ( ph -> ( F |` ( 0 ..^ ( N + 1 ) ) ) = ( ( F |` ( 0 ..^ N ) ) ++ <" ( F ` N ) "> ) ) |