$$\lim_{x \to \infty} \cos{\left(4 x \right)} = \left\langle -1, 1\right\rangle$$ $$\lim_{x \to 0^-} \cos{\left(4 x \right)} = 1$$ More at x→0 from the left $$\lim_{x \to 0^+} \cos{\left(4 x \right)} = 1$$ More at x→0 from the right $$\lim_{x \to 1^-} \cos{\left(4 x \right)} = \cos{\left(4 \right)}$$ More at x→1 from the left $$\lim_{x \to 1^+} \cos{\left(4 x \right)} = \cos{\left(4 \right)}$$ More at x→1 from the right $$\lim_{x \to -\infty} \cos{\left(4 x \right)} = \left\langle -1, 1\right\rangle$$ More at x→-oo