求图片题解---**Text Extraction:** 如如图所示的四棱锥 P-ABCD 中，PA ⊥ 平面 ABCD, BC//AD, AB ⊥ AD. (1) 证明: 平面 PAB ⊥ 平面 PAD; (2) 若 PA = AB = √2, AD = √3+1, BC = 2, P, B, C, D 在同一个球面上，设该球面的球心为 O. (i) 证明: O 在平面 ABCD 上； (ii) 求直线 AC 与直线 PO 所成角的余弦值. **Chart/Diagram Description:** * **Type:** 3D geometric figure (Pyramid). * **Main Elements:** * **Vertices:** Labeled P (apex), A, B, C, D (base vertices). * **Edges:** Straight lines connecting the vertices. * Visible edges: PB, PC, PD, BC, CD. * Hidden (dashed) edges: PA, AB, AD, AC. * **Planes:** The figure represents the pyramid P-ABCD. The base is the quadrilateral ABCD, and the side faces are triangles PAB, PBC, PCD, PDA. * **Labels:** Vertices are labeled P, A, B, C, D. * **Relative Position and Direction:** P is the apex. ABCD is the base plane. PA appears vertical in the diagram, consistent with the text stating PA ⊥ 平面 ABCD. The points A, B, C, D are arranged in a quadrilateral in the base plane. Edges PA, PB, PC, PD connect the apex to the base vertices. The edges AB, BC, CD, DA form the boundary of the base. This describes the geometry problem and the associated diagram.