
theorem Th1212:
Sum digits(2575,10) = 19
proof
  thus Sum digits(2575,10) = Sum <%5,7,5%>+Sum <%2%> by Th1211,AFINSQ_2:55
  .= Sum <%5,7%> + Sum <%5%> + Sum <%2%> by AFINSQ_2:55
  .= (5 + 7) + Sum <%5%> + Sum <%2%> by AFINSQ_2:54
  .= (5 + 7 + 5) + Sum <%2%> by AFINSQ_2:53
  .= 17 + 2 by AFINSQ_2:53
  .= 19;
end;
