共50条信息
已知\(\tan α=2\),则\( \dfrac{\sin α+2\cos α}{\sin α-\cos α} =(\) \()\)
已知\(\cos α= \dfrac{3}{5} \),\(α∈\left( \dfrac{3π}{2},2π\right) \),则\(\cos \left(α- \dfrac{π}{4}\right)= (\) \()\)
若\(\tan \alpha =\cos \alpha \),则\(\dfrac{1}{\sin \alpha }+{{\cos }^{4}}\alpha =\) .
若\(\cos (\dfrac{\pi }{4}-\alpha )=\dfrac{3}{5}\),则\(\sin 2\alpha =(\) \()\)
如图,在\(\triangle ABC\)中,\(AB=3\),\(AC=2\),\(BC=4\),点\(D\)在边\(BC\)上,\(\angle BAD=\)\(45^{\circ}\),则\(\tan \angle CAD\)的值为 .
若\(\sin 2α= \dfrac{2}{3},α∈\left(0,π\right) \),则\(\sin \alpha +\cos \alpha =\)____________.
在\(\triangle ABC\)中,若\(\dfrac{\tan A}{\tan B}=\dfrac{{{a}^{2}}}{{{b}^{2}}}\),则\(\triangle ABC\)的形状是\((\) \()\)
设\(∆ABC \)的内角\(A\),\(B\),\(C\)所对的边分别为\(a\),\(b\),\(c.\)已知\(a=1\),\(b=2\),\(\cos C= \dfrac{1}{4} \).
\((1)\)求\(∆ABC \)的周长;
\((2)\)求\(\cos \left(A-C\right) \)的值.
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