
theorem Th1150:
Sum digits(1525,10) = 13
proof
  thus Sum digits(1525,10) = Sum <%5,2,5%>+Sum <%1%> by Th1149,AFINSQ_2:55
  .= Sum <%5,2%> + Sum <%5%> + Sum <%1%> by AFINSQ_2:55
  .= (5 + 2) + Sum <%5%> + Sum <%1%> by AFINSQ_2:54
  .= (5 + 2 + 5) + Sum <%1%> by AFINSQ_2:53
  .= 12 + 1 by AFINSQ_2:53
  .= 13;
end;
