帮我解答一下这个题---Here is the extracted content from the image: **Question 3:** **Title/Hint:** [Using the Three Perpendiculars Theorem to find dihedral angles] **Question Stem:** As shown in the figure, in triangular pyramid A-BCD, plane ABD ⊥ plane BCD, AB = AD, O is the midpoint of BD. **(1) Prove:** OA ⊥ CD; **(2) If** △OCD is an equilateral triangle with side length 1, point E is on edge AD, DE = 2EA, and the dihedral angle E - BC - D has a measure of 45°, find the volume of triangular pyramid A-BCD. --- **Chart/Diagram Description:** * **Type:** Geometric figure, a 3D representation of a triangular pyramid. * **Main Elements:** * **Points:** * A: Apex of the pyramid. * B, C, D: Vertices of the base triangle BCD. * O: A point on the edge BD, specifically stated as the midpoint of BD. * E: A point on the edge AD. * **Lines/Edges:** * Solid lines: AB, AD, AC, BC, CD, EC. These represent visible edges of the pyramid or connecting lines. * Dashed lines: BD, AO, OC, OE. These represent hidden edges or construction lines. * **Shapes:** * The overall figure is a triangular pyramid A-BCD. * The base is triangle BCD. * Other triangular faces are △ABD, △ABC, △ACD. * Internal triangles shown by construction lines include △AOD, △AOB, △COD, △BOC, △AOE, △OEC, △OED. * **Relative Positions:** * A is positioned above the base △BCD. * O is on the segment BD, specifically its midpoint. * E is on the segment AD, between A and D. * Plane ABD is perpendicular to plane BCD. * Edges AB and AD are equal in length (AB = AD). * Specific relationships like DE = 2EA and the dihedral angle E-BC-D = 45° are mentioned in the text for part (2).