
theorem Th1092:
Sum digits(375,10) = 15
proof
  thus Sum digits(375,10) = Sum <%5,7%>+Sum <%3%> by Th1091,AFINSQ_2:55
  .= (5 + 7) + Sum <%3%> by AFINSQ_2:54
  .= 12 + 3 by AFINSQ_2:53
  .= 15;
end;
