If a quadrilateral has a pair of equal opposite angles and a pair of equal opposite sides, is it a parallelogram?[br]If not, how many shapes (convex or concave) can be formed with such property?[br][br]Geogebra can help us visualize this problem![br][br]Points A, B can be dragged to change the shapes.[br][br]Advanced question: Can you understand how I created this demo? What kind of circle properties did I use?