Question

очень срочно помогите пож

Answer 1

$lim_{x to 0} frac{cos9x-cos5x}{sin9x+sin5x}= lim_{x to 0} frac{-2sinx7x*sin2x}{2sin7x*cos2x}=-lim_{x to 0} frac{sin2x}{cos2x}=-lim_{x to 0} tg2x=0$