
theorem Th1222:
Sum digits(2750,10) = 14
proof
  thus Sum digits(2750,10) = Sum <%0,5,7%>+Sum <%2%> by Th1221,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%7%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%7%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 5 + 7) + Sum <%2%> by AFINSQ_2:53
  .= 12 + 2 by AFINSQ_2:53
  .= 14;
end;
