let seq be Complex_Sequence; ( seq is summable implies ( seq is convergent & lim seq = 0c ) )
assume A1:
seq is summable
; ( seq is convergent & lim seq = 0c )
then
Re (Partial_Sums seq) is convergent
;
then
Partial_Sums (Re seq) is convergent
by Th26;
then A2:
Re seq is summable
;
Im (Partial_Sums seq) is convergent
by A1;
then
Partial_Sums (Im seq) is convergent
by Th26;
then A3:
Im seq is summable
;
then
lim (Im seq) = 0
by SERIES_1:4;
then A4:
Im (lim seq) = 0
by A2, A3, Th42;
lim (Re seq) = 0
by A2, SERIES_1:4;
then
Re (lim seq) = 0
by A2, A3, Th42;
hence
( seq is convergent & lim seq = 0c )
by A2, A3, A4, Lm1, Th42, COMPLEX1:13; verum