
theorem Th515:
Sum digits(1860,10) = 15
proof
  thus Sum digits(1860,10) = Sum <%0,6,8%>+Sum <%1%> by Th514,AFINSQ_2:55
  .= Sum <%0,6%> + Sum <%8%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 6) + Sum <%8%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 6 + 8) + Sum <%1%> by AFINSQ_2:53
  .= 14 + 1 by AFINSQ_2:53
  .= 15;
end;
