
theorem Th805:
Sum digits(1012,10) = 4
proof
  thus Sum digits(1012,10) = Sum <%2,1,0%>+Sum <%1%> by Th804,AFINSQ_2:55
  .= Sum <%2,1%> + Sum <%0%> + Sum <%1%> by AFINSQ_2:55
  .= (2 + 1) + Sum <%0%> + Sum <%1%> by AFINSQ_2:54
  .= (2 + 1 + 0) + Sum <%1%> by AFINSQ_2:53
  .= 3 + 1 by AFINSQ_2:53
  .= 4;
end;
