Drag the points of the triangle to learn more about the relationships between the angle measures and the lengths of the sides of a triangle.

Answer the following questions using the applet. 1.　Can you make a quadrilateral of four sides being 2 cm, 3 cm, 3 cm and 9 cm? Why or why not? 2.　If a quadrilateral has four equal sides, what are its possible shapes? 3.　If a quadrilateral has two pairs of equal opposite sides, what are its possible shapes? 4.　If a quadrilateral has two pairs of equal adjacent sides, what is its shape? 5.　Make the trapezium of the four sides (from top to bottom) being: 　　(a) 4 cm, 4 cm, 4 cm, 6 cm;　　(b) 4 cm, 4 cm, 5 cm, 6 cm; 　　(c) 4 cm, 3 cm, 5 cm, 7 cm;　　(d) 3 cm, 3 cm, 5 cm, 7 cm. 　　What is the characteristic of trapeziums?

Anthony Or, Education Bureau, Hong Kong.