Students move the points around to investigate the angle sum of a quadrilateral. There is also an option to show whether the quadrilateral is convex or concave.
Task 1. Drag the vertices of the shape above to form the shapes below. Pay attention to the angle sum and state the angle sum in each case. (a) Square
(b) Rectangle
(c) Parallelogram
(d) Rhombus
Task 2. What did you notice in each case? What is your explanation for this?
Task 3. What is the angle sum of each triangle below? Join both triangles to form a quadrilateral? What is the angle sum of the quadrilateral formed?
What can you say about the sum of the interior angles of a quadrilateral?