let k be Nat; :: thesis: for D being non empty set
for p being Element of D
for f being FinSequence of D st p in rng f & p .. f > k holds
p in rng (f /^ k)
let D be non empty set ; :: thesis: for p being Element of D
for f being FinSequence of D st p in rng f & p .. f > k holds
p in rng (f /^ k)
let p be Element of D; :: thesis: for f being FinSequence of D st p in rng f & p .. f > k holds
p in rng (f /^ k)
let f be FinSequence of D; :: thesis: ( p in rng f & p .. f > k implies p in rng (f /^ k) )
assume that
A1: p in rng f and
A2: p .. f > k ; :: thesis: p in rng (f /^ k)
p .. f <= len f by A1, FINSEQ_4:31;
then A3: k <= len f by A2, XXREAL_0:2;
A4: k + (p .. (f /^ k)) = p .. f by A1, A2, Th61;
then p .. (f /^ k) <> 0 by A2;
then A5: 1 <= p .. (f /^ k) by NAT_1:14;
len (f /^ k) = (len f) - k by A3, RFINSEQ:def 2;
then A6: (len (f /^ k)) + k = len f ;
k + (p .. (f /^ k)) <= len f by A1, A4, FINSEQ_4:31;
then p .. (f /^ k) <= len (f /^ k) by A6, XREAL_1:8;
then A7: p .. (f /^ k) in dom (f /^ k) by A5, FINSEQ_3:27;
then (f /^ k) /. (p .. (f /^ k)) in rng (f /^ k) by PARTFUN2:4;
then f /. (k + (p .. (f /^ k))) in rng (f /^ k) by A7, FINSEQ_5:30;
hence p in rng (f /^ k) by A1, A4, FINSEQ_5:41; :: thesis: verum