Câu 3: Đặt $\dfrac{1}{x}=t$$\lim \limits_{x\to +\infty} (x+2)\sin \dfrac{2}{x}=\lim \limits_{t\to 0} (2+\dfrac{1}{t})\sin 2t =\lim \limits_{t\to 0}2\sin 2t +\lim \limits_{t\to 0} 2\dfrac{\sin t}{t} \cos t =2$
Câu 3: Đặt $\dfrac{1}{x}=t$$\lim \limits_{x\to +\infty} (x+2)\sin \dfrac{2}{x}=\lim \limits_{t\to 0} (2+\dfrac{1}{t})\sin 2t =\lim \limits_{x\to +\infty} 2\sin 2t +\lim \limits_{x\to +\infty} 2\dfrac{\sin t}{t} \cos t =2$
Câu 3: Đặt $\dfrac{1}{x}=t$$\lim \limits_{x\to +\infty} (x+2)\sin \dfrac{2}{x}=\lim \limits_{t\to 0} (2+\dfrac{1}{t})\sin 2t =\lim \limits_{
t\to
0}2\sin 2t +\lim \limits_{
t\to
0} 2\dfrac{\sin t}{t} \cos t =2$