共50条信息
\((\)Ⅰ\()\)求:\(BC\)的长;\((\)Ⅱ\()\)求\(\triangle DBC\)的面积\(.\)
如图,从气球上测得正前方的河流的两岸,的俯角分别为,,此时气球的高是,则河流的宽度等于\((\) \()\)
\(\triangle ABC\)中,角\(A\),\(B\),\(C\)的对边分别是 \(a\), \(b\), \(c\),已知 \(b\)\(=\) \(c\), \(a\)\({\,\!}^{2}=2\) \(b\)\({\,\!}^{2}(1- \)\(\sin \)\(A)\),则\(A=\)( )
如图,在\(\triangle ABC \)中,\(AB=2 \),\(\cos B= \dfrac{1}{3} \),点\(D \)在线段\(BC \)上\(.\)
\((I)\)若\(∠ADC= \dfrac{3}{4}π \),求\(AD \)的长;
\((II)\)若\(BD=2DC \),\(\triangle ACD \)的面积为\( \dfrac{4}{3} \sqrt{2} \),求\( \dfrac{\sin ∠BAD}{\sin ∠CAD} \)的值.
若\(\left( a+b+c \right)\cdot (b+c-a)=3bc\),且\(\sin A=2\sin B\cos C\),那么\(\Delta ABC\)是\((\) \()\)
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