let D be non empty set ; :: thesis: for f being FinSequence of D
for p being Element of D
for i being Nat holds rng (Replace f,i,p) c= (rng f) \/ {p}

let f be FinSequence of D; :: thesis: for p being Element of D
for i being Nat holds rng (Replace f,i,p) c= (rng f) \/ {p}

let p be Element of D; :: thesis: for i being Nat holds rng (Replace f,i,p) c= (rng f) \/ {p}
let i be Nat; :: thesis: rng (Replace f,i,p) c= (rng f) \/ {p}
reconsider i = i as Element of NAT by ORDINAL1:def 13;
rng <*p*> = {p} by FINSEQ_1:56;
then A1: (rng f) \/ {p} = rng (f ^ <*p*>) by FINSEQ_1:44;
set P = f | (i -' 1);
set Q = f /^ i;
set F = <*(f . i)*>;
per cases ( not i in Seg (len f) or i in Seg (len f) ) ;
suppose not i in Seg (len f) ; :: thesis: rng (Replace f,i,p) c= (rng f) \/ {p}
then ( not 1 <= i or not i <= len f ) ;
then rng (Replace f,i,p) = rng f by Def1;
hence rng (Replace f,i,p) c= (rng f) \/ {p} by A1, FINSEQ_1:42; :: thesis: verum
end;
suppose i in Seg (len f) ; :: thesis: rng (Replace f,i,p) c= (rng f) \/ {p}
then A2: ( 1 <= i & i <= len f ) by FINSEQ_1:3;
then A3: rng (Replace f,i,p) = rng (((f | (i -' 1)) ^ <*p*>) ^ (f /^ i)) by Def1
.= rng ((f | (i -' 1)) ^ (<*p*> ^ (f /^ i))) by FINSEQ_1:45
.= (rng (f | (i -' 1))) \/ (rng (<*p*> ^ (f /^ i))) by FINSEQ_1:44
.= (rng (f | (i -' 1))) \/ ((rng <*p*>) \/ (rng (f /^ i))) by FINSEQ_1:44
.= (rng (f | (i -' 1))) \/ (rng ((f /^ i) ^ <*p*>)) by FINSEQ_1:44
.= rng ((f | (i -' 1)) ^ ((f /^ i) ^ <*p*>)) by FINSEQ_1:44 ;
(rng f) \/ {p} = rng ((((f | (i -' 1)) ^ <*(f . i)*>) ^ (f /^ i)) ^ <*p*>) by A1, A2, FINSEQ_5:87
.= (rng (((f | (i -' 1)) ^ <*(f . i)*>) ^ (f /^ i))) \/ (rng <*p*>) by FINSEQ_1:44
.= (rng ((f | (i -' 1)) ^ (<*(f . i)*> ^ (f /^ i)))) \/ (rng <*p*>) by FINSEQ_1:45
.= ((rng (f | (i -' 1))) \/ (rng (<*(f . i)*> ^ (f /^ i)))) \/ (rng <*p*>) by FINSEQ_1:44
.= ((rng (f | (i -' 1))) \/ ((rng <*(f . i)*>) \/ (rng (f /^ i)))) \/ (rng <*p*>) by FINSEQ_1:44
.= (rng (f | (i -' 1))) \/ (((rng (f /^ i)) \/ (rng <*(f . i)*>)) \/ (rng <*p*>)) by XBOOLE_1:4
.= (rng (f | (i -' 1))) \/ (((rng (f /^ i)) \/ (rng <*p*>)) \/ (rng <*(f . i)*>)) by XBOOLE_1:4
.= ((rng (f | (i -' 1))) \/ ((rng (f /^ i)) \/ (rng <*p*>))) \/ (rng <*(f . i)*>) by XBOOLE_1:4
.= ((rng (f | (i -' 1))) \/ (rng ((f /^ i) ^ <*p*>))) \/ (rng <*(f . i)*>) by FINSEQ_1:44
.= (rng ((f | (i -' 1)) ^ ((f /^ i) ^ <*p*>))) \/ (rng <*(f . i)*>) by FINSEQ_1:44
.= rng (((f | (i -' 1)) ^ ((f /^ i) ^ <*p*>)) ^ <*(f . i)*>) by FINSEQ_1:44 ;
hence rng (Replace f,i,p) c= (rng f) \/ {p} by A3, FINSEQ_1:42; :: thesis: verum
end;
end;