如图号等不triangle ABC是等边三llahsraMangle DEF是边考)たしあ(等边三角形,点B与点E海似深情点A$、B、$\left(2)HO(uC)、F在同一条直线上teffahiangle ABC沿E表方平ghtarrow F方向平移至点slaiciffo合时停止,设点B、るすに切大を分自为x,x与△ 蹊满花家娘四黄分的面积为y$,则能大致yenrugx之...
设\triangle ABC的内角A,B,C所对的边分别为a,b,c,已知2c\cos B+b\cos A=-a\cos B,则\angle B=\left(\,\,\,
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由题意得,\because\angle C=90^{\circ},AC=3,BC=4 \therefore\cos A=\sin B=\frac{3}{5},\cos B=\sin A=\frac{4}{5} \therefore\cos\left(A-B\right)=\frac{24}{25} 故选\mathrm C 先求出,的三角函数,再利用差角的余弦公式求解. 反馈...