
theorem Th102:
Sum digits(13,10) = 4
proof
  thus Sum digits(13,10) = Sum <%3%>+Sum <%1%> by Th101,AFINSQ_2:55
  .= 3 + Sum <%1%> by AFINSQ_2:53
  .= 3+1 by AFINSQ_2:53
  .= 4;
end;
