EIGRP路由协议的可行条件是（）。 A: AD=FD B: AD<FD C: AD>FD D: AD>=FD

利用行列式的性质计算下列行列式的值1 2 0 0 02 5 0 0 0 9 8 1 2 37 6 4 5 65 4 7 8 9

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在四边形ABCD中，→AD＝→DC，且→AC·→BD＝0，则四边形ABCD是（ ）

写一个文法G,使其语言为不以0开头的偶数集。 A: G[S]:S→AB|BA→AD|CB→2|4|6|8｜0C→1|3|5||7|9|B B: G[S]:S→AB|BA→AD|CB→1|2|3|4|5|6|7|8|9C→2|4|6|8｜0 C: G[S]:S→AB|BA→AD|CB→2|4|6|8｜0C→1|2|3|4|5|6|7|8|9D→0|C D: G[S]:S→AB|BA→AD|DB→2|4|6|8｜0D→1|2|3|4|5|6|7|8|9|0

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如图，在梯形ABCD中，AB∥DC，∠D=90°，AD=DC=4，AB=1，F为AD的中点，则点F到BC的距离是（　　） A: 1 B: 2 C: 4 D: 8

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在梯形ABCD中，AD∥BC，AB=DC=AD=6，∠ABC=60°，点E，F分别在线段AD，DC上（点E与点A，D不重合），且∠BEF=120°，设AE=x，DF=y．