Open Middle: Triangle Angles

① This interactive GeoGebra example is an 'Open Middle' style exploration where students manipulate triangle vertices or related angles to investigate angle relationships in triangles. ② Core mathematical concepts include the triangle angle sum theorem, angle measurement and calculation, geometric transformations (rotation), and relationships among interior, exterior, and supplementary angles. ③ Construction highlights: based on the construction summary, the example uses commands such as Ray, Rotate, Angle, Point, Intersect, Segment, and Polygon, along with multiple auxiliary lines (l1-l8), angle variables (α, β, γ), and text objects (text2, text3) to dynamically display angle values. ④ Suitable for middle school geometry lessons or math exploration activities, this resource helps students develop intuition about angle relationships and logical reasoning, and can be used as an open-ended task where students design triangles meeting specific angle conditions.