
theorem Th1204:
Sum digits(2450,10) = 11
proof
  thus Sum digits(2450,10) = Sum <%0,5,4%>+Sum <%2%> by Th1203,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%4%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%4%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 5 + 4) + Sum <%2%> by AFINSQ_2:53
  .= 9 + 2 by AFINSQ_2:53
  .= 11;
end;
