
theorem Th1051:
Sum digits(312,10) = 6
proof
  thus Sum digits(312,10) = Sum <%2,1%>+Sum <%3%> by Th1050,AFINSQ_2:55
  .= (2 + 1) + Sum <%3%> by AFINSQ_2:54
  .= 3 + 3 by AFINSQ_2:53
  .= 6;
end;
