
theorem Th58:
Sum digits(22,10) = 4
proof
  thus Sum digits(22,10) = Sum <%2%>+Sum <%2%> by Th57,AFINSQ_2:55
  .= 2 + Sum <%2%> by AFINSQ_2:53
  .= 2+2 by AFINSQ_2:53
  .= 4;
end;
