(1)设AD=3,AB=AE=2,åDE=DF=1
æè¯â AEB=â DEF=45°,â´BEâ¥EF
âµé¢PBEâ¥é¢BCDE,EFå
å«æ¼é¢BCDE
â´EFâ¥é¢PBE,â´é¢PEFâ¥é¢PBE
(2)è¿æ¥CE,å¾è¡å®çå¾CE=â5
åBEä¸ç¹G,è¿æ¥PG,åPGâ¥é¢BCDE,PG=BG=BE/2=â2
è¿æ¥FG,ç±æ¢¯å½¢ä¸ä½çº¿å®çå¾FG=2
å¾è¡å®çå¾PF=â6
è¿æ¥CG,â GBC=45°,é¦å¼¦å®çå¾CG^2=5,â´PC=â7
PE=2,PC=â7,CE=â5,é¦å¼¦å®çå¾cosCPE=3/2â7
åçcosEPF=2/â6,cosCPF=â6/â7
â´sinEPF=â2/â6,sinCPF=1/â7
设äºé¢è§E-PF-C为x,åcosCPE=cosCPFcosEPF+sinCPFsinEPFcosx,解å¾cosx=-â3/2
â´x=150°
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