
theorem Th172:
Sum digits(75,10) = 12
proof
  thus Sum digits(75,10) = Sum <%5%>+Sum <%7%> by Th171,AFINSQ_2:55
  .= 5 + Sum <%7%> by AFINSQ_2:53
  .= 5+7 by AFINSQ_2:53
  .= 12;
end;
