
theorem Th1004:
Sum digits(1150,10) = 7
proof
  thus Sum digits(1150,10) = Sum <%0,5,1%>+Sum <%1%> by Th1003,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%1%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%1%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 5 + 1) + Sum <%1%> by AFINSQ_2:53
  .= 6 + 1 by AFINSQ_2:53
  .= 7;
end;
