
theorem Th86:
Sum digits(187,10) = 16
proof
  thus Sum digits(187,10) = Sum <%7,8%>+Sum <%1%> by Th85,AFINSQ_2:55
  .= (7 + 8) + Sum <%1%> by AFINSQ_2:54
  .= 15 + 1 by AFINSQ_2:53
  .= 16;
end;
