
theorem Th1126:
Sum digits(1075,10) = 13
proof
  thus Sum digits(1075,10) = Sum <%5,7,0%>+Sum <%1%> by Th1125,AFINSQ_2:55
  .= Sum <%5,7%> + Sum <%0%> + Sum <%1%> by AFINSQ_2:55
  .= (5 + 7) + Sum <%0%> + Sum <%1%> by AFINSQ_2:54
  .= (5 + 7 + 0) + Sum <%1%> by AFINSQ_2:53
  .= 12 + 1 by AFINSQ_2:53
  .= 13;
end;
