
theorem Th139:
Sum digits(28,10) = 10
proof
  thus Sum digits(28,10) = Sum <%8%>+Sum <%2%> by Th138,AFINSQ_2:55
  .= 8 + Sum <%2%> by AFINSQ_2:53
  .= 8+2 by AFINSQ_2:53
  .= 10;
end;
