求解这道题目---**Problem Number:** 13 **Question Stem:** 如图, 已知: AC = AD, BC = BD, 求证: △ABC ≌ △ABD. (As shown in the figure, Given: AC = AD, BC = BD, Prove: △ABC ≌ △ABD.) **Given:** AC = AD BC = BD **Prove:** △ABC ≌ △ABD **Options:** [None] **Other Relevant Text:** [None] **Mathematical Formulas/Equations:** AC = AD BC = BD △ABC ≌ △ABD **Chart/Diagram Description:** * **Type:** Geometric figure (Two triangles sharing a common side). * **Main Elements:** * **Points:** Four points labeled A, B, C, D. Points A and B are connected by a horizontal line segment. Point C is located below the line segment AB. Point D is located above the line segment AB. * **Lines:** Line segments AB, AC, BC, AD, BD. * **Shapes:** The figure is composed of two triangles, △ABC and △ABD, sharing the common side AB. * **Labels and Annotations:** * Points are labeled A, B, C, D. * Side AC is marked with a single short line segment (tick mark). * Side AD is marked with a single short line segment (tick mark), indicating AC = AD. * Side BC is marked with two short line segments (tick marks). * Side BD is marked with two short line segments (tick marks), indicating BC = BD. * **Relative Position and Direction:** Points A and B form a horizontal line segment. C is below AB, and D is above AB. AC and AD connect point A to C and D respectively. BC and BD connect point B to C and D respectively.