Cho hàm số \(y = \dfrac{1}{{2 - \cos x}} + \dfrac{1}{{1 + \cos x}}\) với \(x \in \left( {0;\dfrac{\pi }{2}} \right)\). Kết luận nào sau đây đúng?
A.\(\mathop {min}\limits_{\left( {0;\dfrac{\pi }{2}} \right)} y = \dfrac{4}{3}\)khi \(x = \dfrac{\pi }{3} + k\pi ,\,\,k \in \mathbb{Z}\)
B.\(\mathop {min}\limits_{\left( {0;\dfrac{\pi }{2}} \right)} y = \dfrac{2}{3}\)khi \(x = \dfrac{\pi }{3}\)
C.\(\mathop {min}\limits_{\left( {0;\dfrac{\pi }{2}} \right)} y = \dfrac{2}{3}\)khi \(x = \dfrac{\pi }{3} + k2\pi ,\,\,k \in \mathbb{Z}\)
D.\(\mathop {min}\limits_{\left( {0;\dfrac{\pi }{2}} \right)} y = \dfrac{4}{3}\)khi \(x = \dfrac{\pi }{3}\)
A.\(\mathop {min}\limits_{\left( {0;\dfrac{\pi }{2}} \right)} y = \dfrac{4}{3}\)khi \(x = \dfrac{\pi }{3} + k\pi ,\,\,k \in \mathbb{Z}\)
B.\(\mathop {min}\limits_{\left( {0;\dfrac{\pi }{2}} \right)} y = \dfrac{2}{3}\)khi \(x = \dfrac{\pi }{3}\)
C.\(\mathop {min}\limits_{\left( {0;\dfrac{\pi }{2}} \right)} y = \dfrac{2}{3}\)khi \(x = \dfrac{\pi }{3} + k2\pi ,\,\,k \in \mathbb{Z}\)
D.\(\mathop {min}\limits_{\left( {0;\dfrac{\pi }{2}} \right)} y = \dfrac{4}{3}\)khi \(x = \dfrac{\pi }{3}\)
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