
theorem Th215:
Sum digits(416,10) = 11
proof
  thus Sum digits(416,10) = Sum <%6,1%>+Sum <%4%> by Th214,AFINSQ_2:55
  .= (6 + 1) + Sum <%4%> by AFINSQ_2:54
  .= 7 + 4 by AFINSQ_2:53
  .= 11;
end;
