
theorem Th1318:
Sum digits(4250,10) = 11
proof
  thus Sum digits(4250,10) = Sum <%0,5,2%>+Sum <%4%> by Th1317,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%2%> + Sum <%4%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%2%> + Sum <%4%> by AFINSQ_2:54
  .= (0 + 5 + 2) + Sum <%4%> by AFINSQ_2:53
  .= 7 + 4 by AFINSQ_2:53
  .= 11;
end;
