
theorem Th1334:
Sum digits(4450,10) = 13
proof
  thus Sum digits(4450,10) = Sum <%0,5,4%>+Sum <%4%> by Th1333,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%4%> + Sum <%4%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%4%> + Sum <%4%> by AFINSQ_2:54
  .= (0 + 5 + 4) + Sum <%4%> by AFINSQ_2:53
  .= 9 + 4 by AFINSQ_2:53
  .= 13;
end;
