let f1, f be PartFunc of REAL ,REAL ; :: thesis: ( f1 is divergent_in+infty_to-infty & ex r being Real st
( right_open_halfline r c= (dom f) /\ (dom f1) & ( for g being Real st g in right_open_halfline r holds
f . g <= f1 . g ) ) implies f is divergent_in+infty_to-infty )
assume A1: f1 is divergent_in+infty_to-infty ; :: thesis: ( for r being Real holds
( not right_open_halfline r c= (dom f) /\ (dom f1) or ex g being Real st
( g in right_open_halfline r & not f . g <= f1 . g ) ) or f is divergent_in+infty_to-infty )
given r1 being Real such that A2: ( right_open_halfline r1 c= (dom f) /\ (dom f1) & ( for g being Real st g in right_open_halfline r1 holds
f . g <= f1 . g ) ) ; :: thesis: f is divergent_in+infty_to-infty

A3: now

let r be Real; :: thesis: ex g being Real st
( r < g & g in dom f )
consider g being real number such that
A4: (abs r) + (abs r1) < g by XREAL_1:3;
reconsider g = g as Real by XREAL_0:def 1;
take g = g; :: thesis: ( r < g & g in dom f )
A5: 0 <= abs r1 by COMPLEX1:132;
r <= abs r by ABSVALUE:11;
then 0 + r <= (abs r) + (abs r1) by A5, XREAL_1:9;
hence r < g by A4, XXREAL_0:2; :: thesis: g in dom f
A6: 0 <= abs r by COMPLEX1:132;
r1 <= abs r1 by ABSVALUE:11;
then 0 + r1 <= (abs r) + (abs r1) by A6, XREAL_1:9;
then r1 < g by A4, XXREAL_0:2;
then g in { g2 where g2 is Real : r1 < g2 } ;
then g in right_open_halfline r1 by XXREAL_1:230;
hence g in dom f by A2, XBOOLE_0:def 4; :: thesis: verum

end;

now

X: ( (dom f) /\ (dom f1) c= dom f & (dom f) /\ (dom f1) c= dom f1 ) by XBOOLE_1:17;
A8: (dom f) /\ (right_open_halfline r1) = right_open_halfline r1 by X, A2, XBOOLE_1:1, XBOOLE_1:28;
hence (dom f) /\ (right_open_halfline r1) c= (dom f1) /\ (right_open_halfline r1) by X, A2, XBOOLE_1:1, XBOOLE_1:28; :: thesis: for g being Real st g in (dom f) /\ (right_open_halfline r1) holds
f . g <= f1 . g
let g be Real; :: thesis: ( g in (dom f) /\ (right_open_halfline r1) implies f . g <= f1 . g )
assume g in (dom f) /\ (right_open_halfline r1) ; :: thesis: f . g <= f1 . g
hence f . g <= f1 . g by A2, A8; :: thesis: verum

end;

hence f is divergent_in+infty_to-infty by A1, A3, Th104; :: thesis: verum