
theorem Th141:
Sum digits(42,10) = 6
proof
  thus Sum digits(42,10) = Sum <%2%>+Sum <%4%> by Th140,AFINSQ_2:55
  .= 2 + Sum <%4%> by AFINSQ_2:53
  .= 2+4 by AFINSQ_2:53
  .= 6;
end;
