请讲一下这道题目---**Question 25:** **Question Stem:** 如图，已知线段AB，点C是线段AB外一点，连接AC, ∠CAB = α (90° < α < 180°). 将线段AC沿AB平移得到线段BD. 点P是线段AB上一动点，连接PC, PD. As shown in the figure, given line segment AB, point C is a point outside line segment AB. Connect AC, ∠CAB = α (90° < α < 180°). Translate line segment AC along AB to get line segment BD. Point P is a moving point on line segment AB. Connect PC, PD. **(1)** 依题意在图1中补全图形，并证明：∠CPD = ∠PCA + ∠PDB; (1) According to the problem description, complete the figure in Figure 1, and prove: ∠CPD = ∠PCA + ∠PDB; **(2)** 过点C作直线 l // PD. 在直线 l 上取点 M, 使∠MDC = (1/2) ∠CDP. (2) Draw a line l through point C such that l // PD. Take a point M on line l such that ∠MDC = (1/2) ∠CDP. ① 当α = 120°时，画出图形，并直接用等式表示∠BDM与∠BDP之间的数量关系; ① When α = 120°, draw the figure, and directly express the quantitative relationship between ∠BDM and ∠BDP using an equation; ② 在点P运动的过程中，当点P到直线l的距离最大时，∠BDP的度数是____ (用含α的式子表示). ② In the process of point P's movement, when the distance from point P to line l is maximum, the degree measure of ∠BDP is ____ (expressed in terms of α). **Diagrams:** * **Figure 1:** Geometric figure showing points A, B, C, P. P is on segment AB. Lines AC, BC, CP are drawn. There is a horizontal line segment AB with point P on it, and a point C above. * Points: A, B, C, P. P is between A and B. * Lines: Line segment AB, line segment AC, line segment BC (implied by the problem description of point C outside AB and connecting AC), line segment CP. A horizontal arrow extends from B, suggesting a line extending beyond B. * Labels: A, B, C, P, "图1". * **备用图 (Spare Figure):** Geometric figure showing points A, B, C, P. Similar to Figure 1. * Points: A, B, C, P. P is between A and B. * Lines: Line segment AB, line segment AC, line segment BC (implied), line segment CP. A horizontal arrow extends from B. * Labels: A, B, C, P, "备用图".