
theorem Th587:
Sum digits(2580,10) = 15
proof
  thus Sum digits(2580,10) = Sum <%0,8,5%>+Sum <%2%> by Th586,AFINSQ_2:55
  .= Sum <%0,8%> + Sum <%5%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 8) + Sum <%5%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 8 + 5) + Sum <%2%> by AFINSQ_2:53
  .= 13 + 2 by AFINSQ_2:53
  .= 15;
end;
