∴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.