Giới hạn \(\lim \limits_{x \rightarrow \frac{\pi}{3}} \frac{\sin x-\sqrt{3} \cos x}{2 \cos x-1}\) là
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Lời giải:
Báo saiTa có:
\(\begin{array}{l} \mathop {\lim }\limits_{x \to \frac{\pi }{3}} \frac{{\sin x - \sqrt 3 \cos x}}{{2\cos x - 1}} = \mathop {\lim }\limits_{x \to \frac{\pi }{3}} \frac{{\sin \left( {x - \frac{\pi }{3}} \right)}}{{\cos x - \cos \frac{\pi }{3}}} = \mathop {\lim }\limits_{x \to \frac{\pi }{3}} \frac{{2\sin \left( {\frac{x}{2} - \frac{\pi }{6}} \right)\cos \left( {\frac{x}{2} - \frac{\pi }{6}} \right)}}{{ - 2\sin \left( {\frac{x}{2} + \frac{\pi }{6}} \right)\sin \left( {\frac{x}{2} - \frac{\pi }{6}} \right)}}\\ = \mathop {\lim }\limits_{x \to \frac{\pi }{3}} \frac{{ - \cos \left( {\frac{x}{2} - \frac{\pi }{6}} \right)}}{{\sin \left( {\frac{x}{2} + \frac{\pi }{6}} \right)}} = - \frac{{2\sqrt 3 }}{3} \end{array}\)