
theorem Th897:
Sum digits(2134,10) = 10
proof
  thus Sum digits(2134,10) = Sum <%4,3,1%>+Sum <%2%> by Th896,AFINSQ_2:55
  .= Sum <%4,3%> + Sum <%1%> + Sum <%2%> by AFINSQ_2:55
  .= (4 + 3) + Sum <%1%> + Sum <%2%> by AFINSQ_2:54
  .= (4 + 3 + 1) + Sum <%2%> by AFINSQ_2:53
  .= 8 + 2 by AFINSQ_2:53
  .= 10;
end;
