let D be non empty set ; :: thesis: for f being FinSequence of D
for p being Element of D
for i being Nat st 1 <= i & i <= len f holds
(Replace f,i,p) /. i = p
let f be FinSequence of D; :: thesis: for p being Element of D
for i being Nat st 1 <= i & i <= len f holds
(Replace f,i,p) /. i = p
let p be Element of D; :: thesis: for i being Nat st 1 <= i & i <= len f holds
(Replace f,i,p) /. i = p
let i be Nat; :: thesis: ( 1 <= i & i <= len f implies (Replace f,i,p) /. i = p )
assume ( 1 <= i & i <= len f ) ; :: thesis: (Replace f,i,p) /. i = p
then i in dom f by FINSEQ_3:27;
hence (Replace f,i,p) /. i = p by FUNCT_7:38; :: thesis: verum