
theorem Th78:
Sum digits(143,10) = 8
proof
  thus Sum digits(143,10) = Sum <%3,4%>+Sum <%1%> by Th77,AFINSQ_2:55
  .= (3 + 4) + Sum <%1%> by AFINSQ_2:54
  .= 7 + 1 by AFINSQ_2:53
  .= 8;
end;
