
theorem Th1202:
Sum digits(2425,10) = 13
proof
  thus Sum digits(2425,10) = Sum <%5,2,4%>+Sum <%2%> by Th1201,AFINSQ_2:55
  .= Sum <%5,2%> + Sum <%4%> + Sum <%2%> by AFINSQ_2:55
  .= (5 + 2) + Sum <%4%> + Sum <%2%> by AFINSQ_2:54
  .= (5 + 2 + 4) + Sum <%2%> by AFINSQ_2:53
  .= 11 + 2 by AFINSQ_2:53
  .= 13;
end;
