
theorem Th567:
Sum digits(2380,10) = 13
proof
  thus Sum digits(2380,10) = Sum <%0,8,3%>+Sum <%2%> by Th566,AFINSQ_2:55
  .= Sum <%0,8%> + Sum <%3%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 8) + Sum <%3%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 8 + 3) + Sum <%2%> by AFINSQ_2:53
  .= 11 + 2 by AFINSQ_2:53
  .= 13;
end;
