优优班--学霸训练营 > 知识点挑题
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            • 1.
              在\(\triangle ABC\)中,\(\cos \dfrac {C}{2}= \dfrac { \sqrt {5}}{5}\),\(BC=1\),\(AC=5\),则\(AB=(\)  \()\)
              A.\(4 \sqrt {2}\)
              B.\( \sqrt {30}\)
              C.\( \sqrt {29}\)
              D.\(2 \sqrt {5}\)
            • 2.
              \(\triangle ABC\)的内角\(A\),\(B\),\(C\)的对边分别为\(a\),\(b\),\(c.\)已知\(b\sin C+c\sin B=4a\sin B\sin C\),\(b^{2}+c^{2}-a^{2}=8\),则\(\triangle ABC\)的面积为 ______ .
            • 3.
              若\(\triangle ABC\)的面积为\( \dfrac { \sqrt {3}}{4}(a^{2}+c^{2}-b^{2})\),且\(∠C\)为钝角,则\(∠B=\) ______ ;\( \dfrac {c}{a}\)的取值范围是 ______ .
            • 4.

              在\(\vartriangle ABC\)中,\(B=\dfrac{\pi }{4}\),\(BC\)边上的高等于\(\dfrac{1}{3}BC\),则\(\cos A=\) (    )

              A.\(\dfrac{3\sqrt{10}}{10}\)
              B.\(\dfrac{\sqrt{10}}{10}\)
              C.\(-\dfrac{\sqrt{10}}{10}\)
              D.\(-\dfrac{3\sqrt{10}}{10}\)
            • 5.
              \(\triangle ABC\)的内角\(A\),\(B\),\(C\)的对边分别为\(a\),\(b\),\(c\),已知\(C=60^{\circ}\),\(b= \sqrt {6}\),\(c=3\),则\(A=\) ______
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