
theorem Th653:
Sum digits(3240,10) = 9
proof
  thus Sum digits(3240,10) = Sum <%0,4,2%>+Sum <%3%> by Th652,AFINSQ_2:55
  .= Sum <%0,4%> + Sum <%2%> + Sum <%3%> by AFINSQ_2:55
  .= (0 + 4) + Sum <%2%> + Sum <%3%> by AFINSQ_2:54
  .= (0 + 4 + 2) + Sum <%3%> by AFINSQ_2:53
  .= 6 + 3 by AFINSQ_2:53
  .= 9;
end;
