\(\lim\limits_{x\rightarrow4}sin\left(x-4\right)tan\left(\frac{\pi x}{8}\right)\\ =\lim\limits_{x\rightarrow4}\frac{sin\left(x-4\right)}{cot\left(\frac{\pi x}{8}\right)}\\ =\lim\limits_{x\rightarrow4}\frac{cos\left(x-4\right)}{-\frac{\pi}{8}\frac{1}{sin^2\left(\frac{\pi x}{8}\right)}}=\frac{-8}{\pi}\)
Dong cuoi dung quy tac L'hospital do ban