如图,在同一平面内将两个全等的等腰Rt△ABC和△AFG摆放在一起,A为公共顶点,∠BAC=∠AGF=90°,若△ABC固定不动,△AFG绕点A旋转,AF、AG与边BC的交点分别为D、E(点D不与点B重合,点E不与点C重合).则下列四对三角形:①△ABE与△DCA;②△ACD与△EAD;③△EAB与△EAD;④△ABD与△ECA,其中一定相似的有()

如图,△ABC和△DEF是两个全等的等腰直角三角形,∠BAC=∠EDF=90°,△DEF的顶点E与△ABC的斜边BC的中点重合.将△DEF绕点E旋转,旋转过程中,线段DE与线段AB相交于点P,线段EF与射线CA相交于点Q.当点Q在线段CA的延长线上时,若BP=a,CQ=a时,则P,Q两点间的距离为()(用含a的代数式表示).

如图,在直角梯形ABCD中,AB=16,AD=3,BC=5,AB⊥BC,AD∥BC,若AB边上存在P点,使△PAD与△PBC相似.则AP的长是__________.

如图,把一个矩形纸片OABC放入平面直角坐标系中,使OA,OC分别落在x轴、y轴上,连接OB,将纸片OABC沿OB折叠,使点A落在点A′的位置上.若OB=5,,则点A′的坐标为        .

—Where’s your brother now,Bob?—I saw him        in the street a moment ago and I told him         .

       out your love. The world will become a nicer place to live in.

—I feel tired and sleepy.—Why not stop      for a while?

We can’t work out the physics problem. Can you tell us        ?

      a book in the library, enter a key word into the computer.

—Why are you so excited?—Peter invited me         on a trip to Yuntai Montain.