7.如图,在四棱锥P−ABCDP-ABCDP−ABCD中,四边形ABCDABCDABCD是菱形,PA=PCPA=PCPA=PC,EEE为PBPBPB的中点.(1)求证:PD//PD//PD//面AECAECAEC;(2)求证:平面AEC⊥AEC\botAEC⊥平面PDBPDBPDB.