
theorem Th1166:
Sum digits(1825,10) = 16
proof
  thus Sum digits(1825,10) = Sum <%5,2,8%>+Sum <%1%> by Th1165,AFINSQ_2:55
  .= Sum <%5,2%> + Sum <%8%> + Sum <%1%> by AFINSQ_2:55
  .= (5 + 2) + Sum <%8%> + Sum <%1%> by AFINSQ_2:54
  .= (5 + 2 + 8) + Sum <%1%> by AFINSQ_2:53
  .= 15 + 1 by AFINSQ_2:53
  .= 16;
end;
