利用洛必达法则lim(x->0)(ln tan7x)/(ln tan2x)= lim(x->0)7 sec²7x / tan7x/ [ 2 sec²2x / tan2x ]= lim(x->0) (7/2)(sin2xcos2x) / (sin7x cos7x)= lim(x->0) (7/2)(sin2x / sin7x)= 1...