以A为原点,AB所在直线为x轴,AD所在直线为y轴,AP所在直线为z轴建立空间直角坐标系,则A(0,0,0),B(2,0,0),C(2,4,0),D(0,4,0),E(0,2,1),P(0,0,2).∴ AB =(2,0,0), AD =(0,4,0), AP =(0,0,2), CD =(-2,0,0), AE =(0,2,1), AC =(2,4,0).(1)设平面AEC的法向量 n =(x,y,z),令z=1,则 n =(x,y,1).由