let f be PartFunc of REAL,REAL; :: thesis: for r being Real holds
( ( f is divergent_in-infty_to+infty & r > 0 implies r (#) f is divergent_in-infty_to+infty ) & ( f is divergent_in-infty_to+infty & r < 0 implies r (#) f is divergent_in-infty_to-infty ) & ( f is divergent_in-infty_to-infty & r > 0 implies r (#) f is divergent_in-infty_to-infty ) & ( f is divergent_in-infty_to-infty & r < 0 implies r (#) f is divergent_in-infty_to+infty ) )

let r be Real; :: thesis: ( ( f is divergent_in-infty_to+infty & r > 0 implies r (#) f is divergent_in-infty_to+infty ) & ( f is divergent_in-infty_to+infty & r < 0 implies r (#) f is divergent_in-infty_to-infty ) & ( f is divergent_in-infty_to-infty & r > 0 implies r (#) f is divergent_in-infty_to-infty ) & ( f is divergent_in-infty_to-infty & r < 0 implies r (#) f is divergent_in-infty_to+infty ) )
thus ( f is divergent_in-infty_to+infty & r > 0 implies r (#) f is divergent_in-infty_to+infty ) :: thesis: ( ( f is divergent_in-infty_to+infty & r < 0 implies r (#) f is divergent_in-infty_to-infty ) & ( f is divergent_in-infty_to-infty & r > 0 implies r (#) f is divergent_in-infty_to-infty ) & ( f is divergent_in-infty_to-infty & r < 0 implies r (#) f is divergent_in-infty_to+infty ) )
proof
assume that
A1: f is divergent_in-infty_to+infty and
A2: r > 0 ; :: thesis: r (#) f is divergent_in-infty_to+infty
A3: now :: thesis: for seq being Real_Sequence st seq is divergent_to-infty & rng seq c= dom (r (#) f) holds
(r (#) f) /* seq is divergent_to+infty
end;
now :: thesis: for r1 being Real ex g being Real st
( g < r1 & g in dom (r (#) f) )
let r1 be Real; :: thesis: ex g being Real st
( g < r1 & g in dom (r (#) f) )

consider g being Real such that
A7: ( g < r1 & g in dom f ) by A1;
take g = g; :: thesis: ( g < r1 & g in dom (r (#) f) )
thus ( g < r1 & g in dom (r (#) f) ) by A7, VALUED_1:def 5; :: thesis: verum
end;
hence r (#) f is divergent_in-infty_to+infty by A3; :: thesis: verum
end;
thus ( f is divergent_in-infty_to+infty & r < 0 implies r (#) f is divergent_in-infty_to-infty ) :: thesis: ( ( f is divergent_in-infty_to-infty & r > 0 implies r (#) f is divergent_in-infty_to-infty ) & ( f is divergent_in-infty_to-infty & r < 0 implies r (#) f is divergent_in-infty_to+infty ) )
proof
assume that
A8: f is divergent_in-infty_to+infty and
A9: r < 0 ; :: thesis: r (#) f is divergent_in-infty_to-infty
A10: now :: thesis: for seq being Real_Sequence st seq is divergent_to-infty & rng seq c= dom (r (#) f) holds
(r (#) f) /* seq is divergent_to-infty
end;
now :: thesis: for r1 being Real ex g being Real st
( g < r1 & g in dom (r (#) f) )
let r1 be Real; :: thesis: ex g being Real st
( g < r1 & g in dom (r (#) f) )

consider g being Real such that
A14: ( g < r1 & g in dom f ) by A8;
take g = g; :: thesis: ( g < r1 & g in dom (r (#) f) )
thus ( g < r1 & g in dom (r (#) f) ) by A14, VALUED_1:def 5; :: thesis: verum
end;
hence r (#) f is divergent_in-infty_to-infty by A10; :: thesis: verum
end;
thus ( f is divergent_in-infty_to-infty & r > 0 implies r (#) f is divergent_in-infty_to-infty ) :: thesis: ( f is divergent_in-infty_to-infty & r < 0 implies r (#) f is divergent_in-infty_to+infty )
proof
assume that
A15: f is divergent_in-infty_to-infty and
A16: r > 0 ; :: thesis: r (#) f is divergent_in-infty_to-infty
A17: now :: thesis: for seq being Real_Sequence st seq is divergent_to-infty & rng seq c= dom (r (#) f) holds
(r (#) f) /* seq is divergent_to-infty
end;
now :: thesis: for r1 being Real ex g being Real st
( g < r1 & g in dom (r (#) f) )
let r1 be Real; :: thesis: ex g being Real st
( g < r1 & g in dom (r (#) f) )

consider g being Real such that
A21: ( g < r1 & g in dom f ) by A15;
take g = g; :: thesis: ( g < r1 & g in dom (r (#) f) )
thus ( g < r1 & g in dom (r (#) f) ) by A21, VALUED_1:def 5; :: thesis: verum
end;
hence r (#) f is divergent_in-infty_to-infty by A17; :: thesis: verum
end;
assume that
A22: f is divergent_in-infty_to-infty and
A23: r < 0 ; :: thesis: r (#) f is divergent_in-infty_to+infty
A24: now :: thesis: for seq being Real_Sequence st seq is divergent_to-infty & rng seq c= dom (r (#) f) holds
(r (#) f) /* seq is divergent_to+infty
end;
now :: thesis: for r1 being Real ex g being Real st
( g < r1 & g in dom (r (#) f) )
let r1 be Real; :: thesis: ex g being Real st
( g < r1 & g in dom (r (#) f) )

consider g being Real such that
A28: ( g < r1 & g in dom f ) by A22;
take g = g; :: thesis: ( g < r1 & g in dom (r (#) f) )
thus ( g < r1 & g in dom (r (#) f) ) by A28, VALUED_1:def 5; :: thesis: verum
end;
hence r (#) f is divergent_in-infty_to+infty by A24; :: thesis: verum