如图,在底面为正方形的四棱锥P﹣ABCD中,PA=PB=PC=PD=AB=2,点E为棱PA的中点,则异面直线BE与PD所成角的余弦值为____
This is my ____ (brother) basketball. He loves sports.
若x,y为实数,且|x﹣2|+(y+1)2=0,则x-y的值是 ____