 reserve Rseq, Rseq1, Rseq2 for Function of [:NAT,NAT:],REAL;

theorem lm74:
  Partial_Sums(Rseq1 + Rseq2) = Partial_Sums(Rseq1) + Partial_Sums(Rseq2)
proof
   Partial_Sums(Rseq1+Rseq2)
    = Partial_Sums_in_cod2(Partial_Sums_in_cod1(Rseq1)
                 +Partial_Sums_in_cod1(Rseq2)) by thADD;
   hence thesis by thADD;
end;
