
theorem Th1124:
Sum digits(1050,10) = 6
proof
  thus Sum digits(1050,10) = Sum <%0,5,0%>+Sum <%1%> by Th1123,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%0%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%0%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 5 + 0) + Sum <%1%> by AFINSQ_2:53
  .= 5 + 1 by AFINSQ_2:53
  .= 6;
end;
