橙色线段相等，求蓝色角度数 ---**Textual Information:** * Title/Category: 几何构造 (Geometric Construction) * Question Stem: 求蓝色角度数 (Find the value of the blue angle) **Chart/Diagram Description:** * **Type:** Geometric figure (Triangle with internal segments). * **Main Elements:** * A triangle with vertices (implied). Let's label the top vertex A, the bottom left vertex B, and the bottom right vertex C. * A point D is located on side AB. * A point E is located on side AC. * Line segment CD connects point C to point D. * Line segment BE connects point B to point E. * The angle at vertex A (∠BAC) is marked as 20 degrees. * Segments AD, DB, and BC are colored orange. This visual cue strongly suggests that these three segments have equal length: AD = DB = BC. * The angle ∠ADC, formed by segment CD and side AB (specifically AD), is marked with a blue arc and shaded blue. This is the angle requested in the question. * There is also a blue shaded region at the intersection point of segments CD and BE, indicating another angle, but the angle at D is clearly marked with an arc and seems to be the target angle. * **Colors:** * Orange: Segments AD, DB, BC. Angle arc at A. * White: Segments AC, CD, BE. Sides AB and AC. * Blue: Angle arc and shading at ∠ADC. Shading at the intersection of CD and BE. * **Angles:** * ∠BAC = 20° (marked with orange arc). * ∠ADC is the blue angle to be determined (marked with blue arc). * **Assumed Property (based on color):** AD = DB = BC.