(a) proof: AP∑ plane EFG

(ii) Evidence: BC ⊥ Germany.

answer

Proof: (1) As shown in the figure, connect FG,

F and g are the midpoint of PD and AD, respectively.

∴AP∥FG，

FG again? EFG aircraft, the associated press is not included in EFG aircraft,

∴AP∥ plane EFG ..

(ii)∫ABCD is a square, ∴BC⊥DC,

∵PD⊥ bottom ABCD, ∴BC⊥PD,

∫PD∩DC = D，

∴BC⊥ planar PDC,

Germany again? Plane PDC,

∴BC⊥DE.

analyse

(I) connecting FG to get AP∨FG, which can prove AP∨ plane EFG. ..

(2) BC⊥DC is a square, BC⊥PD is perpendicular to the straight line and plane, so BC⊥ plane PDC can be proved.