
theorem Th549:
Sum digits(2200,10) = 4
proof
  thus Sum digits(2200,10) = Sum <%0,0,2%>+Sum <%2%> by Th548,AFINSQ_2:55
  .= Sum <%0,0%> + Sum <%2%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 0) + Sum <%2%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 0 + 2) + Sum <%2%> by AFINSQ_2:53
  .= 2 + 2 by AFINSQ_2:53
  .= 4;
end;
