
theorem Th1108:
Sum digits(775,10) = 19
proof
  thus Sum digits(775,10) = Sum <%5,7%>+Sum <%7%> by Th1107,AFINSQ_2:55
  .= (5 + 7) + Sum <%7%> by AFINSQ_2:54
  .= 12 + 7 by AFINSQ_2:53
  .= 19;
end;
