2.如圖,CA⊥AB,垂足為點(diǎn)A,AB=8cm,AC=4cm,射線BM⊥AB,垂足為點(diǎn)B,一動(dòng)點(diǎn)E從點(diǎn)A出發(fā)以2cm/s的速度沿射線AN運(yùn)動(dòng),點(diǎn)D為射線BM上一動(dòng)點(diǎn),隨著點(diǎn)E運(yùn)動(dòng)而運(yùn)動(dòng),且始終保持ED=CB,當(dāng)點(diǎn)E離開點(diǎn)A后,運(yùn)動(dòng)幾秒時(shí),△DEB與△BCA全等?