
theorem Th1246:
Sum digits(3150,10) = 9
proof
  thus Sum digits(3150,10) = Sum <%0,5,1%>+Sum <%3%> by Th1245,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%1%> + Sum <%3%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%1%> + Sum <%3%> by AFINSQ_2:54
  .= (0 + 5 + 1) + Sum <%3%> by AFINSQ_2:53
  .= 6 + 3 by AFINSQ_2:53
  .= 9;
end;
