set RVO = RV - (Omega --> K);
consider g2 being Function such that
A2:
g2 = chi (((RV - (Omega --> K)) " [.0,+infty.[),Omega)
;
g2 is random_variable of F, Borel_Sets
proof
rng g2 c= {0,1}
by RELAT_1:def 19, A2;
then
rng g2 c= REAL
by H0;
then
(
g2 is
Function of
(dom g2),
REAL &
dom g2 = Omega )
by FUNCT_2:2, FUNCT_2:def 1, A2;
then reconsider g2 =
g2 as
Function of
Omega,
REAL ;
for
x being
set st
x in Borel_Sets holds
g2 " x in F
proof
let x be
set ;
( x in Borel_Sets implies g2 " x in F )
assume
x in Borel_Sets
;
g2 " x in F
then reconsider x =
x as
Element of
Borel_Sets ;
per cases
( ( 1 in x & 0 in x ) or ( 1 in x & not 0 in x ) or ( not 1 in x & 0 in x ) or ( not 1 in x & not 0 in x ) )
;
suppose SB1:
( not 1
in x &
0 in x )
;
g2 " x in F
for
x2 being
object holds
(
x2 in g2 " x iff
x2 in Omega \ ((RV - (Omega --> K)) " [.0,+infty.[) )
proof
let x2 be
object ;
( x2 in g2 " x iff x2 in Omega \ ((RV - (Omega --> K)) " [.0,+infty.[) )
thus
(
x2 in g2 " x implies
x2 in Omega \ ((RV - (Omega --> K)) " [.0,+infty.[) )
( x2 in Omega \ ((RV - (Omega --> K)) " [.0,+infty.[) implies x2 in g2 " x )
assume ll:
x2 in Omega \ ((RV - (Omega --> K)) " [.0,+infty.[)
;
x2 in g2 " x
then L0:
(
x2 in Omega & not
x2 in (RV - (Omega --> K)) " [.0,+infty.[ )
by XBOOLE_0:def 5;
reconsider x2 =
x2 as
Element of
Omega by XBOOLE_0:def 5, ll;
ll:
Omega = dom g2
by FUNCT_2:def 1;
g2 . x2 in x
by SB1, L0, A2, FUNCT_3:def 3;
hence
x2 in g2 " x
by ll, FUNCT_1:def 7;
verum
end; then P1:
g2 " x = Omega \ ((RV - (Omega --> K)) " [.0,+infty.[)
by TARSKI:2;
reconsider Omega =
Omega as
Event of
F by PROB_1:5;
P3:
[.0,+infty.[ is
Event of
Borel_Sets
by FINANCE1:3;
RV - (Omega --> K) is
random_variable of
F,
Borel_Sets
by FINANCE3:11;
then
RV - (Omega --> K) is_random_variable_on F,
Borel_Sets
by RANDOM_3:def 1;
then
(RV - (Omega --> K)) " [.0,+infty.[ is
Event of
F
by P3;
then
Omega \ ((RV - (Omega --> K)) " [.0,+infty.[) is
Event of
F
by PROB_1:24;
hence
g2 " x in F
by P1;
verum end; end;
end;
then
g2 is_random_variable_on F,
Borel_Sets
;
hence
g2 is
random_variable of
F,
Borel_Sets
by RANDOM_3:def 1;
verum
end;
then reconsider g2 = g2 as random_variable of F, Borel_Sets ;
set RVO = RV - (Omega --> K);
reconsider RVO = RV - (Omega --> K) as random_variable of F, Borel_Sets by FINANCE3:11;
set CO = Call-Option (RV,K);
Call-Option (RV,K) = g2 (#) RVO
proof
q1:
for
c being
object st
c in dom (Call-Option (RV,K)) holds
(Call-Option (RV,K)) . c = (g2 . c) * (RVO . c)
proof
let c be
object ;
( c in dom (Call-Option (RV,K)) implies (Call-Option (RV,K)) . c = (g2 . c) * (RVO . c) )
assume
c in dom (Call-Option (RV,K))
;
(Call-Option (RV,K)) . c = (g2 . c) * (RVO . c)
then reconsider c =
c as
Element of
Omega ;
(Call-Option (RV,K)) . c = (g2 . c) * (RVO . c)
proof
per cases
( c in RVO " [.0,+infty.[ or not c in RVO " [.0,+infty.[ )
;
suppose ASSJJ00:
not
c in RVO " [.0,+infty.[
;
(Call-Option (RV,K)) . c = (g2 . c) * (RVO . c)K1:
(
c in Omega & not
c in RVO " [.0,+infty.[ )
by ASSJJ00;
ASSJJ0:
c in RVO " ].-infty,0.[
proof
( not
c in dom RVO or not
RVO . c in [.0,+infty.[ )
by ASSJJ00, FUNCT_1:def 7;
then
( not
c in Omega or not
RVO . c in [.0,+infty.[ )
by FUNCT_2:def 1;
then
(
RV . c in ].-infty,+infty.[ &
-infty < RVO . c &
RVO . c < 0 )
by XXREAL_1:224, XXREAL_0:12, XXREAL_0:9, XXREAL_1:3;
then
(
c in dom RVO &
RVO . c in ].-infty,0.[ )
by K1, FUNCT_2:def 1, XXREAL_1:4;
hence
c in RVO " ].-infty,0.[
by FUNCT_1:def 7;
verum
end; ZW0:
g2 . c = 0
by A2, ASSJJ00, FUNCT_3:def 3;
(
c in dom RVO &
RVO . c in ].-infty,0.[ )
by ASSJJ0, FUNCT_1:def 7;
then
(
-infty < RVO . c &
RVO . c < 0 )
by XXREAL_1:4;
hence
(Call-Option (RV,K)) . c = (g2 . c) * (RVO . c)
by ZW0, FINANCE3:def 5;
verum end; end;
end;
hence
(Call-Option (RV,K)) . c = (g2 . c) * (RVO . c)
;
verum
end;
W1:
(
dom (Call-Option (RV,K)) = Omega &
dom g2 = Omega &
dom RVO = Omega )
by FUNCT_2:def 1;
for
x being
object st
x in dom (Call-Option (RV,K)) holds
(Call-Option (RV,K)) . x = (g2 (#) RVO) . x
hence
Call-Option (
RV,
K)
= g2 (#) RVO
by W1;
verum
end;
hence
Call-Option (RV,K) is random_variable of F, Borel_Sets
by FINANCE2:25; verum