你是一个中国中学老师，向同学讲解这道题目---**Extraction Content:** **Question Stem:** 19. 如图，在Rt△ABC中，∠ACB=90°，AB=2√5，AC=2，分别以点A，B为圆心，大于1/2 AB的长为半径画弧，两弧分别交于点M和N，作直线MN分别交AB，BC于点D，E，连接CD，AE。 **Chart Description:** * **Type:** Geometric figure. * **Main Elements:** * **Points:** A, B, C, D, E, M, N. * **Triangle:** Right-angled triangle ABC, with the right angle at C. * **Lines:** Straight line segments AC, BC, AB, CD, AE, MN. The line MN is shown intersecting AB at D and BC at E. Points M and N are located on opposite sides of the line AB. There are arrows indicating directions from M and N, but their significance isn't explicitly stated beyond defining the line MN. * **Relative Position:** Point C is above the line AB. Point D is on the line segment AB. Point E is on the line segment BC. Points M and N are shown to define the line MN, which appears to be the perpendicular bisector of AB, although this is implied by the construction description rather than explicitly labeled. Line MN is roughly vertical in the diagram, intersecting AB at D and extending upwards towards M and downwards towards N. **Sub-questions:** (1) 求CD的长； (2) 求△ACE的周长。