
theorem Th260:
Sum digits(425,10) = 11
proof
  thus Sum digits(425,10) = Sum <%5,2%>+Sum <%4%> by Th259,AFINSQ_2:55
  .= (5 + 2) + Sum <%4%> by AFINSQ_2:54
  .= 7 + 4 by AFINSQ_2:53
  .= 11;
end;
