
theorem Th1228:
Sum digits(2850,10) = 15
proof
  thus Sum digits(2850,10) = Sum <%0,5,8%>+Sum <%2%> by Th1227,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%8%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%8%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 5 + 8) + Sum <%2%> by AFINSQ_2:53
  .= 13 + 2 by AFINSQ_2:53
  .= 15;
end;
