
theorem Th1226:
Sum digits(2825,10) = 17
proof
  thus Sum digits(2825,10) = Sum <%5,2,8%>+Sum <%2%> by Th1225,AFINSQ_2:55
  .= Sum <%5,2%> + Sum <%8%> + Sum <%2%> by AFINSQ_2:55
  .= (5 + 2) + Sum <%8%> + Sum <%2%> by AFINSQ_2:54
  .= (5 + 2 + 8) + Sum <%2%> by AFINSQ_2:53
  .= 15 + 2 by AFINSQ_2:53
  .= 17;
end;
