
theorem Th699:
Sum digits(3700,10) = 10
proof
  thus Sum digits(3700,10) = Sum <%0,0,7%>+Sum <%3%> by Th698,AFINSQ_2:55
  .= Sum <%0,0%> + Sum <%7%> + Sum <%3%> by AFINSQ_2:55
  .= (0 + 0) + Sum <%7%> + Sum <%3%> by AFINSQ_2:54
  .= (0 + 0 + 7) + Sum <%3%> by AFINSQ_2:53
  .= 7 + 3 by AFINSQ_2:53
  .= 10;
end;
