
theorem Th1144:
Sum digits(1425,10) = 12
proof
  thus Sum digits(1425,10) = Sum <%5,2,4%>+Sum <%1%> by Th1143,AFINSQ_2:55
  .= Sum <%5,2%> + Sum <%4%> + Sum <%1%> by AFINSQ_2:55
  .= (5 + 2) + Sum <%4%> + Sum <%1%> by AFINSQ_2:54
  .= (5 + 2 + 4) + Sum <%1%> by AFINSQ_2:53
  .= 11 + 1 by AFINSQ_2:53
  .= 12;
end;
