
theorem Th815:
Sum digits(1144,10) = 10
proof
  thus Sum digits(1144,10) = Sum <%4,4,1%>+Sum <%1%> by Th814,AFINSQ_2:55
  .= Sum <%4,4%> + Sum <%1%> + Sum <%1%> by AFINSQ_2:55
  .= (4 + 4) + Sum <%1%> + Sum <%1%> by AFINSQ_2:54
  .= (4 + 4 + 1) + Sum <%1%> by AFINSQ_2:53
  .= 9 + 1 by AFINSQ_2:53
  .= 10;
end;
