let f1, f2 be PartFunc of REAL,REAL; ( f1 is divergent_in+infty_to+infty & f2 is divergent_in+infty_to+infty & ( for r being Real ex g being Real st
( r < g & g in (dom f1) /\ (dom f2) ) ) implies ( f1 + f2 is divergent_in+infty_to+infty & f1 (#) f2 is divergent_in+infty_to+infty ) )
assume that
A1:
f1 is divergent_in+infty_to+infty
and
A2:
f2 is divergent_in+infty_to+infty
and
A3:
for r being Real ex g being Real st
( r < g & g in (dom f1) /\ (dom f2) )
; ( f1 + f2 is divergent_in+infty_to+infty & f1 (#) f2 is divergent_in+infty_to+infty )
A4:
now let seq be
Real_Sequence;
( seq is divergent_to+infty & rng seq c= dom (f1 + f2) implies (f1 + f2) /* seq is divergent_to+infty )assume that A5:
seq is
divergent_to+infty
and A6:
rng seq c= dom (f1 + f2)
;
(f1 + f2) /* seq is divergent_to+infty A7:
dom (f1 + f2) = (dom f1) /\ (dom f2)
by A6, Lm2;
rng seq c= dom f2
by A6, Lm2;
then A8:
f2 /* seq is
divergent_to+infty
by A2, A5, Def7;
rng seq c= dom f1
by A6, Lm2;
then
f1 /* seq is
divergent_to+infty
by A1, A5, Def7;
then
(f1 /* seq) + (f2 /* seq) is
divergent_to+infty
by A8, Th35;
hence
(f1 + f2) /* seq is
divergent_to+infty
by A6, A7, RFUNCT_2:23;
verum end;
A9:
now let seq be
Real_Sequence;
( seq is divergent_to+infty & rng seq c= dom (f1 (#) f2) implies (f1 (#) f2) /* seq is divergent_to+infty )assume that A10:
seq is
divergent_to+infty
and A11:
rng seq c= dom (f1 (#) f2)
;
(f1 (#) f2) /* seq is divergent_to+infty A12:
dom (f1 (#) f2) = (dom f1) /\ (dom f2)
by A11, Lm3;
rng seq c= dom f2
by A11, Lm3;
then A13:
f2 /* seq is
divergent_to+infty
by A2, A10, Def7;
rng seq c= dom f1
by A11, Lm3;
then
f1 /* seq is
divergent_to+infty
by A1, A10, Def7;
then
(f1 /* seq) (#) (f2 /* seq) is
divergent_to+infty
by A13, Th37;
hence
(f1 (#) f2) /* seq is
divergent_to+infty
by A11, A12, RFUNCT_2:23;
verum end;
hence
f1 + f2 is divergent_in+infty_to+infty
by A4, Def7; f1 (#) f2 is divergent_in+infty_to+infty
hence
f1 (#) f2 is divergent_in+infty_to+infty
by A9, Def7; verum