
theorem Th915:
Sum digits(2354,10) = 14
proof
  thus Sum digits(2354,10) = Sum <%4,5,3%>+Sum <%2%> by Th914,AFINSQ_2:55
  .= Sum <%4,5%> + Sum <%3%> + Sum <%2%> by AFINSQ_2:55
  .= (4 + 5) + Sum <%3%> + Sum <%2%> by AFINSQ_2:54
  .= (4 + 5 + 3) + Sum <%2%> by AFINSQ_2:53
  .= 12 + 2 by AFINSQ_2:53
  .= 14;
end;
