以A为原点,AB,AC,AP所在直线分别为x轴、y轴、z轴建立空间直角坐标系,由AB=AC=1,PA=2,得A(0,0,0),B(1,0,0),C(0,1,0),P(0,0,2),D(
,0,0),E
,F
,
∴
=(0,0,2),
=
,
=
,设面DEF的法向量为n=(x,y,z).
则由
得
取z=1,则n=(2,0,1),设PA与平面DEF所成角为θ,则sin θ=
=
.
以A为原点,AB,AC,AP所在直线分别为x轴、y轴、z轴建立空间直角坐标系,由AB=AC=1,PA=2,得A(0,0,0),B(1,0,0),C(0,1,0),P(0,0,2),D(
,0,0),E
,F
,
∴
=(0,0,2),
=
,
=
,设面DEF的法向量为n=(x,y,z).
则由
得
取z=1,则n=(2,0,1),设PA与平面DEF所成角为θ,则sin θ=
=
.