共50条信息
已知\(\sin \alpha -\cos \alpha =-\dfrac{1}{5}\),则\(\sin 2\alpha \)的值为 \((\) \()\)
已知函数\(f(x)=\dfrac{\sin 2x+{2}{{\cos }^{2}}x}{\cos x}\).
\((\)Ⅰ\()\)求\(f(x)\)的定义域及\(f(\dfrac{{ }\!\!\pi\!\!{ }}{{4}})\)的值;
\((\)Ⅱ\()\)求\(f(x)\)在\((0,\dfrac{{ }\!\!\pi\!\!{ }}{2})\)上的单调递增区间.
若\(α∈(\dfrac{\mathrm{ }\!\!\pi\!\!{ }}{2},π)\),则\({3\cos 2}\alpha =\sqrt{2}{\sin }\left( \dfrac{\mathrm{ }\!\!\pi\!\!{ }}{4}-\alpha \right)\),则\(\sin 2α\)的值为
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