
theorem Th1138:
Sum digits(1325,10) = 11
proof
  thus Sum digits(1325,10) = Sum <%5,2,3%>+Sum <%1%> by Th1137,AFINSQ_2:55
  .= Sum <%5,2%> + Sum <%3%> + Sum <%1%> by AFINSQ_2:55
  .= (5 + 2) + Sum <%3%> + Sum <%1%> by AFINSQ_2:54
  .= (5 + 2 + 3) + Sum <%1%> by AFINSQ_2:53
  .= 10 + 1 by AFINSQ_2:53
  .= 11;
end;
