请将图中的数学问题的详细解题步骤，录制成中文（字幕或语音的）视频---**Problem Identifier:** 例题 3 **Question Stem:** 如图, 在 △ABC 中, ∠A : ∠B = 1 : 2, CD 是 ∠ACB 的角平分线, CE 是 △ABC 的高, 求 ∠DCE 的度数. **Translation of Question Stem:** As shown in the figure, in △ABC, ∠A : ∠B = 1 : 2, CD is the angle bisector of ∠ACB, CE is the altitude of △ABC, find the measure of ∠DCE. **Mathematical Formulas/Equations:** ∠A : ∠B = 1 : 2 **Chart/Diagram Description:** * **Type:** Geometric figure - Triangle. * **Main Elements:** * **Shape:** Triangle ABC. * **Points:** Vertices A, B, C. Points D and E are on the line segment AB. * **Lines:** Line segments AC, BC, AB forming the triangle. Line segment CD drawn from C to D. Line segment CE drawn from C to E. * **Angles:** ∠A, ∠B, ∠ACB are the interior angles of the triangle. ∠ACD and ∠BCD are the angles formed by the angle bisector CD. ∠AEC and ∠BEC are right angles (indicated by the square symbol at E). ∠DCE is the angle between CD and CE. * **Annotations:** Points A, B, C, D, E are labeled. There is a right angle symbol at point E on the line segment AB, indicating CE ⊥ AB. * **Relative Position and Direction:** E and D are located on the side AB. The order of points on AB from left to right appears to be A, E, D, B in the diagram, although the exact relative positions of E and D may vary depending on the specific angles. CE is shown as the altitude from C to AB. CD is shown as an interior line segment from C to AB. CD is the angle bisector of ∠ACB. CE is perpendicular to AB.