- Whose home is ______ from school, Alice's or Daisy's?
- Alice's, I think.
A:far
B:farther
C:farthest
D:the farthest
有____个三角形
(Ⅰ)求证:PB⊥AD;
(Ⅱ)求直线PC与平面PAB所成的角θ的正弦值.