
theorem Th895:
Sum digits(2112,10) = 6
proof
  thus Sum digits(2112,10) = Sum <%2,1,1%>+Sum <%2%> by Th894,AFINSQ_2:55
  .= Sum <%2,1%> + Sum <%1%> + Sum <%2%> by AFINSQ_2:55
  .= (2 + 1) + Sum <%1%> + Sum <%2%> by AFINSQ_2:54
  .= (2 + 1 + 1) + Sum <%2%> by AFINSQ_2:53
  .= 4 + 2 by AFINSQ_2:53
  .= 6;
end;
