
theorem Th226:
Sum digits(51,10) = 6
proof
  thus Sum digits(51,10) = Sum <%1%>+Sum <%5%> by Th225,AFINSQ_2:55
  .= 1 + Sum <%5%> by AFINSQ_2:53
  .= 1+5 by AFINSQ_2:53
  .= 6;
end;
