共50条信息
在\(\triangle ABC\)中,角\(A\),\(B\),\(B\)所对的边分别为\(a\),\(b\),\(c\),若\(c-a\cos B=(2a-b)\cos A\),\(\Delta ABC\)的形状为__________\(;\)
已知角\(\theta \)的顶点与原点重合,始边与\(x\)轴的正半轴重合,终边在直线\(3x-5y=0\)上,则\(\tan \theta +\sin (\dfrac{7\pi }{2}+2\theta )=\)( )
已知函数\(f\left(x\right)=4\tan x\sin \left( \dfrac{π}{2}-x\right)\cos \left(x- \dfrac{π}{3}\right)- \sqrt{3} \)
\((1)\)求\(f\left(x\right) \)的定义域与最小正周期;
\((2)\)讨论\(f\left(x\right) \)在区间\(\left[- \dfrac{π}{4}, \dfrac{π}{4}\right] \)上的单调性。
设函数\(f(x){=}\sin(2x{-}\dfrac{\pi}{2})\),则\(f(x)\)是\(({ })\)
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\(f(x)= \dfrac{\cos ^{2}(nπ+x)·\sin ^{2}(nπ-x)}{\cos ^{2}[(2n+1)π-x]}(n∈Z)\).
\((1)\)化简\(f(x)\)的表达式;
\((2)\)求\(f\left( \left. \dfrac{π}{2 016} \right. \right)+f\left( \left. \dfrac{1 007π}{2 016} \right. \right)\)的值.
\(\cos({-}300^{{∘}}){=}(\) \()\)
已知角\(α \)的终边在第二象限,且与单位圆交于点\(P\left(m, \dfrac{ \sqrt{15}}{4}\right) \).
\((1)\)求实数\(m\)的值;
\((2)\)求\(\dfrac{\sin \left(α- \dfrac{π}{2}\right)}{\sin \left(π+α\right)-\sin \left( \dfrac{3π}{2}-α\right)+1} \)的值.
在\(\triangle ABC\)中,\(\cos (\dfrac{\mathrm{ }\!\!\pi\!\!{ }}{4}+A)=\dfrac{5}{13}\),则\(\sin 2A=\)________.
已知\(a{=}\sin\dfrac{2\pi}{7}{,}b{=}\cos\dfrac{12\pi}{7}{,}c{=}\tan\dfrac{9\pi}{7}\),则\(({ })\)
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