let F be finite set ; :: thesis: for A being FinSequence of bool F
for i being Element of NAT
for x being set st i in dom A holds
Cut (A,i,x) is Reduction of A,i
let A be FinSequence of bool F; :: thesis: for i being Element of NAT
for x being set st i in dom A holds
Cut (A,i,x) is Reduction of A,i
let i be Element of NAT ; :: thesis: for x being set st i in dom A holds
Cut (A,i,x) is Reduction of A,i
let x be set ; :: thesis: ( i in dom A implies Cut (A,i,x) is Reduction of A,i )
set f = Cut (A,i,x);
A1: dom (Cut (A,i,x)) = dom A by Def2;
then A2: for j being Element of NAT st j in dom A & j <> i holds
A . j = (Cut (A,i,x)) . j by Def2;
assume i in dom A ; :: thesis: Cut (A,i,x) is Reduction of A,i
then (Cut (A,i,x)) . i = (A . i) \ {x} by A1, Def2;
hence Cut (A,i,x) is Reduction of A,i by A1, A2, Def5; :: thesis: verum