The bottom of p-abcd is square, the bottom of PD ⊥ is ABCD, and the point E is on the edge Pb, Proving plane AEC ⊥ plane PDB When PD = AB twice the root and E is the midpoint of Pb, the angle between AE and plane PDB is obtained,

The bottom surface ABCD is square, AC ⊥ bdpd ⊥ bottom surface ABCD, AC ⊥ PD so, AC ⊥ plane pdbac # 8834; plane AEC so, plane AEC ⊥ plane PDB, let o be the midpoint of BD, connect EO because AC ⊥ plane PDB

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