
theorem Th302:
Sum digits(342,10) = 9
proof
  thus Sum digits(342,10) = Sum <%2,4%>+Sum <%3%> by Th301,AFINSQ_2:55
  .= (2 + 4) + Sum <%3%> by AFINSQ_2:54
  .= 6 + 3 by AFINSQ_2:53
  .= 9;
end;
