
theorem Th1214:
Sum digits(2625,10) = 15
proof
  thus Sum digits(2625,10) = Sum <%5,2,6%>+Sum <%2%> by Th1213,AFINSQ_2:55
  .= Sum <%5,2%> + Sum <%6%> + Sum <%2%> by AFINSQ_2:55
  .= (5 + 2) + Sum <%6%> + Sum <%2%> by AFINSQ_2:54
  .= (5 + 2 + 6) + Sum <%2%> by AFINSQ_2:53
  .= 13 + 2 by AFINSQ_2:53
  .= 15;
end;
