共50条信息
在\(\triangle ABC\)中,已知内角\(A\),\(B\),\(C\)对边分别是\(a\),\(b\),\(c\),且\(2c\cos B=2a+b\).
在\(∆ABC \)中,内角\(A \),\(B \),\(C \)的对边分别为\(a \),\(b \),\(c \),且\(c\cos B+b\cos C=2a\cos A \).
\((1)\)求\(A \);
\((2)\)若\(a=2 \),且\(∆ABC \)的面积为\(\sqrt{3} \),求\(∆ABC \)的周长.
已知:\({\sin }^{2}{30}^{^{\circ}}+{\sin }^{2}90^{\circ}+{\sin }^{2}150^{\circ}= \dfrac{3}{2}{\sin }^{2}5^{\circ}+{\sin }^{2}60^{\circ}+{\sin }^{2}125^{\circ}= \dfrac{3}{2} .\)通过观察上述两等式的规律,写出一般性的命题:_____________________\( = \dfrac{3}{2} \).
在\(\triangle ABC\)中,“\(A > B\)”是“\(\cos 2A < \cos 2B\)”的( )
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