
theorem Th1306:
Sum digits(4100,10) = 5
proof
  thus Sum digits(4100,10) = Sum <%0,0,1%>+Sum <%4%> by Th1305,AFINSQ_2:55
  .= Sum <%0,0%> + Sum <%1%> + Sum <%4%> by AFINSQ_2:55
  .= (0 + 0) + Sum <%1%> + Sum <%4%> by AFINSQ_2:54
  .= (0 + 0 + 1) + Sum <%4%> by AFINSQ_2:53
  .= 1 + 4 by AFINSQ_2:53
  .= 5;
end;
