Cho hàm số y=f(x) = 1- cos 3xcos5xccos7x/ sin^27x Tính lim x->0 f(x)

Ta có limx→0fx=limx→01−cos3xcos5xcos7xsin27x

=limx→01−cos3x+cos3x−cos3xcos5x+cos3xcos5x−cos3xcos5xcos7xsin27x

=limx→01−cos3xsin27x+limx→0cos3x1−cos5xsin27x+limx→0cos3xcos5x1−cos7xsin27x

=limx→02sin23x2sin27x+limx→02sin25x2sin27x+limx→02sin27x2sin27x=294+254+49449=8398