
theorem Th1172:
Sum digits(1925,10) = 17
proof
  thus Sum digits(1925,10) = Sum <%5,2,9%>+Sum <%1%> by Th1171,AFINSQ_2:55
  .= Sum <%5,2%> + Sum <%9%> + Sum <%1%> by AFINSQ_2:55
  .= (5 + 2) + Sum <%9%> + Sum <%1%> by AFINSQ_2:54
  .= (5 + 2 + 9) + Sum <%1%> by AFINSQ_2:53
  .= 16 + 1 by AFINSQ_2:53
  .= 17;
end;
