tinh gioi han khi x dan toi 0

N

ngtuan96

$$\frac{cos(\frac{\pi}{2}cosx)}{sin^2(\frac{x}{2})}=\frac{sin(\frac{\pi}{2}(1-cosx))}{\frac{1-cosx}{2}}=\pi.\frac{sin(\pi(\frac{1-cosx}{2}))}{\pi(\frac{1-cosx}{2})}$$
$$\Longrightarrow \lim_{x\rightarrow 0}\frac{cos(\frac{\pi}{2}cosx)}{sin^2(\frac{x}{2})}=\pi$$
 
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