Cho \(\sin \alpha = \frac{1}{{\sqrt {10} }}\,\,\,\,\left( {0 < \alpha < \frac{\pi }{2}} \right).\) Tính \(\cos \alpha \,\,;\,\,\tan \alpha .\)
A.\(\cos \alpha = \frac{3}{{\sqrt {10} }}\,\,;\,\,\tan \alpha = \frac{1}{3}\)
B.\(\cos \alpha = \pm \frac{3}{{\sqrt {10} }}\,\,;\,\,\tan \alpha = \pm \frac{1}{3}\)
C.\(\cos \alpha = \frac{2}{{\sqrt {10} }}\,\,;\,\,\tan \alpha = \frac{1}{2}\)
D.\(\cos \alpha = \pm \frac{2}{{\sqrt {10} }}\,\,;\,\,\tan \alpha = \pm \frac{1}{2}\)
A.\(\cos \alpha = \frac{3}{{\sqrt {10} }}\,\,;\,\,\tan \alpha = \frac{1}{3}\)
B.\(\cos \alpha = \pm \frac{3}{{\sqrt {10} }}\,\,;\,\,\tan \alpha = \pm \frac{1}{3}\)
C.\(\cos \alpha = \frac{2}{{\sqrt {10} }}\,\,;\,\,\tan \alpha = \frac{1}{2}\)
D.\(\cos \alpha = \pm \frac{2}{{\sqrt {10} }}\,\,;\,\,\tan \alpha = \pm \frac{1}{2}\)
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Hóa Học lớp 12
