Question

Вычислите предел функции lim(x->0) (cos9x-cos5x)/(sin9x+sin5x)

Answer 1

Lim(x->0) (cos9x-cos5x)/(sin9x+sin5x)=
lim(x->0) (-2sin7x*sin2x)/(2sin7x*cos2x)=
lim(x->0) (-tg2x)=-tg(2*0)=-tg0=0