
theorem Th1188:
Sum digits(2175,10) = 15
proof
  thus Sum digits(2175,10) = Sum <%5,7,1%>+Sum <%2%> by Th1187,AFINSQ_2:55
  .= Sum <%5,7%> + Sum <%1%> + Sum <%2%> by AFINSQ_2:55
  .= (5 + 7) + Sum <%1%> + Sum <%2%> by AFINSQ_2:54
  .= (5 + 7 + 1) + Sum <%2%> by AFINSQ_2:53
  .= 13 + 2 by AFINSQ_2:53
  .= 15;
end;
