
theorem Th647:
Sum digits(3180,10) = 12
proof
  thus Sum digits(3180,10) = Sum <%0,8,1%>+Sum <%3%> by Th646,AFINSQ_2:55
  .= Sum <%0,8%> + Sum <%1%> + Sum <%3%> by AFINSQ_2:55
  .= (0 + 8) + Sum <%1%> + Sum <%3%> by AFINSQ_2:54
  .= (0 + 8 + 1) + Sum <%3%> by AFINSQ_2:53
  .= 9 + 3 by AFINSQ_2:53
  .= 12;
end;
