let F be FinSequence of COMPLEX ; :: thesis: Sum (- F) = - (Sum F)
thus Sum (- F) = addcomplex $$ (compcomplex * F) by SEQ_4:def 11
.= compcomplex . (addcomplex $$ F) by SEQ_4:68, SEQ_4:69, SETWOP_2:42
.= - (Sum F) by BINOP_2:def 1 ; :: thesis: verum