
theorem Th865:
Sum digits(1738,10) = 19
proof
  thus Sum digits(1738,10) = Sum <%8,3,7%>+Sum <%1%> by Th864,AFINSQ_2:55
  .= Sum <%8,3%> + Sum <%7%> + Sum <%1%> by AFINSQ_2:55
  .= (8 + 3) + Sum <%7%> + Sum <%1%> by AFINSQ_2:54
  .= (8 + 3 + 7) + Sum <%1%> by AFINSQ_2:53
  .= 18 + 1 by AFINSQ_2:53
  .= 19;
end;
