共50条信息
\( \dfrac{2\cos 80^{\circ}+\cos 160^{\circ}}{\cos 70^{\circ}}\)的值是( )
设\(\Delta ABC\)的内角\(A,B,C\)的对边分别为\(a,b,c\) ,\((a+b+c)(a-b+c)=ac\) .
\((1)\)求\(B\)
\((2)\)若\(\sin A\sin C=\dfrac{\sqrt{3}-1}{4}\) ,求\(C\) .
在锐角\(\Delta ABC\)中,角\(A,B,C\)的对边分别为\(a,b,c\),且\(a\cos B+b\cos A=2c\cos C\).
\((\)Ⅰ\()\)求角\(C\);
\((\)Ⅱ\()\)若\(c=2\sqrt{3}\),求\(\Delta ABC\)周长的取值范围.
进入组卷