$$\lim_{x \to \infty}\left(\frac{4 x}{\sin{\left(2 x \right)}}\right)$$
$$\lim_{x \to 0^-}\left(\frac{4 x}{\sin{\left(2 x \right)}}\right) = 2$$
More at x→0 from the left$$\lim_{x \to 0^+}\left(\frac{4 x}{\sin{\left(2 x \right)}}\right) = 2$$
More at x→0 from the right$$\lim_{x \to 1^-}\left(\frac{4 x}{\sin{\left(2 x \right)}}\right) = \frac{4}{\sin{\left(2 \right)}}$$
More at x→1 from the left$$\lim_{x \to 1^+}\left(\frac{4 x}{\sin{\left(2 x \right)}}\right) = \frac{4}{\sin{\left(2 \right)}}$$
More at x→1 from the right$$\lim_{x \to -\infty}\left(\frac{4 x}{\sin{\left(2 x \right)}}\right)$$
More at x→-oo