Cho \( \cos \alpha = \frac{1}{3}; \alpha \in \left( { \pi ;2 \pi } \right) \) tính giá trị \( \sin \alpha = \)? Và \(A = \frac{{1 - 4{{ \sin }^2}x + {{ \cos }^2}x}}{{3 + {{ \sin }^2}x - 4 \cos 2x}}. \)
A.\(\sin \alpha = - \frac{2\sqrt{2}}{3} \,\,;\,\, A = - \frac{4}{11}\)
B.\(\sin \alpha = \frac{2\sqrt{2}}{3} \,\,;\,\, A = \frac{4}{11}\)
C.\(\sin \alpha = - \frac{\sqrt{2}}{3} \,\,;\,\, A = - \frac{2}{11}\)
D.\(\sin \alpha = \frac{\sqrt{2}}{3} \,\,;\,\, A = \frac{2}{11}\)
A.\(\sin \alpha = - \frac{2\sqrt{2}}{3} \,\,;\,\, A = - \frac{4}{11}\)
B.\(\sin \alpha = \frac{2\sqrt{2}}{3} \,\,;\,\, A = \frac{4}{11}\)
C.\(\sin \alpha = - \frac{\sqrt{2}}{3} \,\,;\,\, A = - \frac{2}{11}\)
D.\(\sin \alpha = \frac{\sqrt{2}}{3} \,\,;\,\, A = \frac{2}{11}\)
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Hóa Học lớp 12
