共50条信息
在\(\triangle ABC\)中,\(2a\cos A+b\cos C+c\cos B=0\),则角\(A\)的大小为( )
代数式\(\sin 15{}^\circ \cos 75{}^\circ +\cos 15{}^\circ \sin 105{}^\circ =\)________.
设函数\(f(x){=}\sin(2x{-}\dfrac{\pi}{2})\),则\(f(x)\)是\(({ })\)
已知\(\alpha\)为锐角,且\(\sin\alpha{=}\dfrac{4}{5}\),则\(\cos(\pi{-}\alpha){=}({ })\)
函数\(y{=}\sin(\dfrac{\pi}{3}{-}2x)\)的单调减区间是\(({ })\)
\(\dfrac{2\cos {{10}^{\circ }}-\cos {{70}^{\circ }}}{\cos {{20}^{\circ }}}\)的值是\((\) \()\)
在斜三角形\(ABC\)中,\(\sin A=- \sqrt{2}\cos B·\cos C \),且\(\tan B·\tan C=1- \sqrt{2} \),则角\(A\)的值为( )
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