
theorem Th563:
Sum digits(2340,10) = 9
proof
  thus Sum digits(2340,10) = Sum <%0,4,3%>+Sum <%2%> by Th562,AFINSQ_2:55
  .= Sum <%0,4%> + Sum <%3%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 4) + Sum <%3%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 4 + 3) + Sum <%2%> by AFINSQ_2:53
  .= 7 + 2 by AFINSQ_2:53
  .= 9;
end;
