
theorem Th487:
Sum digits(1580,10) = 14
proof
  thus Sum digits(1580,10) = Sum <%0,8,5%>+Sum <%1%> by Th486,AFINSQ_2:55
  .= Sum <%0,8%> + Sum <%5%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 8) + Sum <%5%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 8 + 5) + Sum <%1%> by AFINSQ_2:53
  .= 13 + 1 by AFINSQ_2:53
  .= 14;
end;
