?AB?GH?AD
Q在Rt?APH中，?PAH?45o,??APH?90o??PAH?45o,?AH?PH
?AH?PH?BG?GE
QPG?GH?PH,DH?AD?AH,?PG?DH又Q?DHP??PGE?90o
??DPH??PEG?SAS? ??HDP??GPE
??DPE?180o??HPD??GPE?180o???HPD??HDP??90o
??PDE为等腰直角三角形
（2）Q在Rt?APH中，AP?x,?AH?PH?22x,?DH?2?x， 2222?2??2?2x?2?x?x?22x?4 ?在Rt?DPH中，PD2?DH2?PH2??????2???2????Q?PDE为等腰直角三角形， ?S?PDE?111PD?PE?PD2?x2?2x?2,0?x?2 222??o（3）在等腰直角三角形?PDE中，PD?PE,?DPE?90,??PED??PDE?45，
o当四边形PBED是梯形时，只有可能PB//DE,
??PBE??FEC,?BPE??PED?45o
QPB?PE,??PBE??PEB?180??BPE?67.5o
2??EFC?180o??FEC??ACB?67.5o ??EFC??FEC,?CE?CF
Q?PFD??EFC?67.5o,??DPF?180o??PDF??PFD?67.5o ??CDP?180o??DPF??PCD?67.5o,??CDP??DPF
?CP?CD
?AP?x?AC?CP?AC?CD?22?2
?EC?BC?BE?BC?2BG?2?2x?22?2
9
?PF?AC?AP?CF?4?22
10
