共50条信息
已知\(\sin \left( \left. \dfrac{π}{4}-x \right. \right)= \dfrac{3}{5}\),则\(\sin 2x\)的值为\((\) \()\)
在\(\triangle ABC\)中,角\(A\),\(B\),\(C\)所对的边分别为\(a\),\(b\),\(c\),若\({\,\!}_{b}^{c} < \cos A\),则\(\triangle ABC\)为
已知\({\sin }\left( \alpha +\dfrac{\pi }{6} \right)=\dfrac{2\sqrt{5}}{5}\),则\({\cos }\left( \dfrac{\pi }{3}-\alpha \right)=\)( )
若\(\sin (\dfrac{{ }\!\!\pi\!\!{ }}{4}-x)=-\dfrac{1}{5}\),则\(\cos (\dfrac{5{ }\!\!\pi\!\!{ }}{4}+x)\)的值等于\((\) \()\)
设\(α∈\left( \left. 0, \dfrac{π}{2} \right. \right)\),\(β∈\left( \left. 0, \dfrac{π}{2} \right. \right)\),且\(\tan α= \dfrac{1+\sin β}{\cos β}\),则( )
已知\(\sin \left( x+\dfrac{\pi }{3} \right)=\dfrac{1}{3}\),则\(\sin \left( \dfrac{5\pi }{3}-x \right)-\cos \left( 2x-\dfrac{\pi }{3} \right)\)的值为__.
已知\(
已知函数\(f(x)=\sin \left( \left. x- \dfrac{π}{2} \right. \right)(x∈R)\),下面结论错误的是\((\) \()\)
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