∴BC⊥PA

∫AB is the diameter of the circle O, and C is the point on the circle O..

∴BC⊥AC

∫PA∩AC = A

∴BC⊥ Plane packaging

∫AF, PC in the plane PAC.

∴AF⊥BC,BC⊥PC

∵AF⊥PC

BC∩PC=C

∴AF⊥ Plane PBC

∵PB in PBC plane

∴PB⊥AF

∵PB⊥AE,AE∩AF=A

Pb ⊥ Aircraft Company

∴PB⊥EF

∴∠FEP=90？

BC⊥PC,∠PCB=90？ ，∠BPC=∠EPF

∴ Triangle PEF is similar to triangle PBC.