执笔抒情(2)证明：方法一：在Rt△CEF中，CE 1,EF 2
CF2 CE2 EF2 12 22
5
························································································································6分 CF ·
在Rt△DEF中，DE 4，EF 2
DF2 DE2 EF2 42 22
20
DF 由（1）得C 1， 1 ，D 4， 1
CD 5 CD2 52 25
·································································································· 7分 CF2 DF2 CD2 ·
CFD 90° ··············································································································· 8分 CF⊥DF·
55方法二：由 （1
）知AF ，AC
44 AF AC ················································································································· 6分
同理：BF BD ACF AFC AC∥EF
ACF CFO AFC CFO ······································································································ 7分 同理： BFD OFD
CFD OFC OFD 90° 即CF⊥DF ················································································································ 8分
（3）存在.
解：如图3，作PM⊥x轴，垂足为点M ··········· 9分 又
PQ⊥OP
Rt△OPM∽Rt△OQP
PMOM
PQOP
PQPM
···················································· 10分
OPOM
图3
