对图片内容生成讲解视频---**Extraction Content:** **Question Stem:** 1. 如图, 已知△ABC是正三角形, EA、CD 都垂直于平面ABC, 且 EA=AB=2a, DC=a, F 是 BE 的中点, 求证: **(Translation: As shown in the figure, it is known that △ABC is an equilateral triangle, EA and CD are both perpendicular to the plane ABC, and EA=AB=2a, DC=a, F is the midpoint of BE, prove:)** **Diagram Description:** * **Type:** 3D geometric diagram. * **Main Elements:** * **Points:** Labeled points A, B, C, D, E, F, M. * **Lines:** Solid lines connecting A-B, B-C, C-D, D-E, E-A, A-F, F-B, B-E. Dashed lines forming the triangle A-B-C, a dashed line from A to C, and a line segment labeled M near point A, seemingly connecting to A. * **Shapes:** Triangle ABC is shown as a base. Vertical lines EA and CD extend upwards from A and C respectively. Points E, A, B, F form some structure. Points C, D, B form some structure. Points E, A, C, D form some structure. * **Relative Position and Direction:** EA is shown as a vertical line segment from A. CD is shown as a vertical line segment from C. Both are described in the text as perpendicular to the plane ABC. F is located on the line segment BE. Point M is located near point A. Triangle ABC appears to be in a horizontal plane. * **Labels and Annotations:** Points are labeled A, B, C, D, E, F, M.