lim x\(\rightarrow o\) \(\dfrac{sin3x}{tan2x}\), lim x\(\rightarrow o\) \(\dfrac{cos\left(x-\dfrac{\pi}{2}\right)}{sin4x}\) , limx\(\rightarrow o\)\(\dfrac{cos\left(\dfrac{\pi}{2}cos2x\right)}{sĩnx^2}\) , lim x\(\rightarrow\)o \(\dfrac{\sqrt{cosx}-1}{xsinx}\)