
theorem Th887:
Sum digits(2024,10) = 8
proof
  thus Sum digits(2024,10) = Sum <%4,2,0%>+Sum <%2%> by Th886,AFINSQ_2:55
  .= Sum <%4,2%> + Sum <%0%> + Sum <%2%> by AFINSQ_2:55
  .= (4 + 2) + Sum <%0%> + Sum <%2%> by AFINSQ_2:54
  .= (4 + 2 + 0) + Sum <%2%> by AFINSQ_2:53
  .= 6 + 2 by AFINSQ_2:53
  .= 8;
end;
