Construction of Quadrilaterals and Their Interior Angles

This applet demonstrates the basic geometric construction and properties of a quadrilateral. By defining four vertices A, B, C, and D, it constructs a polygon and dynamically displays its four sides (a, b, c, d) and four interior angles (α, β, γ, δ). Utilizing GeoGebra's Polygon and Angle tools, it visually presents the relationships between the side lengths and angles of a quadrilateral, making it an effective interactive teaching tool for foundational geometry concepts. Students can drag the vertices to deform the quadrilateral in real time and observe how the side lengths and interior angles change accordingly. The applet reinforces the key theorem that the sum of the interior angles of any quadrilateral always equals 360 degrees, regardless of how the shape is altered. Learners can also investigate special types of quadrilaterals—such as rectangles, parallelograms, trapezoids, and kites—by adjusting the positions of the vertices to recognize distinguishing properties. This hands-on exploration helps students move beyond rote memorization and develop an intuitive understanding of geometric relationships, fostering deeper conceptual learning in plane geometry.