
theorem Th1344:
Sum digits(4575,10) = 21
proof
  thus Sum digits(4575,10) = Sum <%5,7,5%>+Sum <%4%> by Th1343,AFINSQ_2:55
  .= Sum <%5,7%> + Sum <%5%> + Sum <%4%> by AFINSQ_2:55
  .= (5 + 7) + Sum <%5%> + Sum <%4%> by AFINSQ_2:54
  .= (5 + 7 + 5) + Sum <%4%> by AFINSQ_2:53
  .= 17 + 4 by AFINSQ_2:53
  .= 21;
end;
