
theorem Th819:
Sum digits(1188,10) = 18
proof
  thus Sum digits(1188,10) = Sum <%8,8,1%>+Sum <%1%> by Th818,AFINSQ_2:55
  .= Sum <%8,8%> + Sum <%1%> + Sum <%1%> by AFINSQ_2:55
  .= (8 + 8) + Sum <%1%> + Sum <%1%> by AFINSQ_2:54
  .= (8 + 8 + 1) + Sum <%1%> by AFINSQ_2:53
  .= 17 + 1 by AFINSQ_2:53
  .= 18;
end;
