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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 11: giúp em tìm GTLN GTNN với ạ y=2 / ( 3 + cosx )

Toán Lớp 11: giúp em tìm GTLN GTNN với ạ y=2 / ( 3 + cosx )

Comments ( 1 )

  1. $\begin{array}{l} y = \dfrac{2}{{3 + \cos x}}\\  – 1 \le \cos x \le 1\\  \Rightarrow 2 \le 3 + \cos x \le 4\\  \Rightarrow \dfrac{1}{2} \le y \le 1\\  \Rightarrow \left\{ \begin{array}{l} \min y = \dfrac{1}{2} \Rightarrow \cos x = 1\\ \max y = 1 \Rightarrow \cos x =  – 1 \end{array} \right.\\  \Rightarrow \left\{ \begin{array}{l} \min y = \dfrac{1}{2} \Rightarrow x = k2\pi \\ \max y = 1 \Rightarrow x = \pi  + k2\pi  \end{array} \right.\left( {k \in \mathbb{Z}} \right) \end{array}$  

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222-9+11+12:2*14+14 = ? ( )

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