如图，在□ABCD中，AC平分∠DAB，AB = 2，则□ABCD的周长为(           )

      A poor woodcutter and his wife lived in the forest in a small hut.   1 was so small that there was space only for him and his wife to sleep.
      One cold night, somebody knocked 2 the door. The woodcutter asked his wife  3the door and let the stranger in. She said, “ But there is no space.” The man laughed 4 said, “ Two can sleep well, three can sit.” And then the woman opened the door. The stranger5 to come in, and they all sat telling stories to each other.
     Then came 6 knock. The woodcutter told the stranger, “Friend, open the door.” And the man said, “But there is no space.” The woodcutter said, “If three persons can sit comfortably, four persons can sit a little7 than before.”
The stranger opened the door, and a man entered. Suddenly, a strange knock 8 did not seem to be human's! The woodcutter said, “Open the door. I know who 9.  It is my donkey.”
    Everyone said, “  10is the donkey going to stand?” The man said, “Right now we are sitting, when the donkey comes in, we will all stand.”

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对称轴为：____

顶点坐标为：____．