
theorem Th447:
Sum digits(1180,10) = 10
proof
  thus Sum digits(1180,10) = Sum <%0,8,1%>+Sum <%1%> by Th446,AFINSQ_2:55
  .= Sum <%0,8%> + Sum <%1%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 8) + Sum <%1%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 8 + 1) + Sum <%1%> by AFINSQ_2:53
  .= 9 + 1 by AFINSQ_2:53
  .= 10;
end;
