[b]1) Overview[/b]
It is observed that students may have problems on drawing quadrilaterals with non-standard orientations on the grid, such as parallelograms without horizontal or vertical sides, or rhombuses without horizontal or vertical diagonals. This applet enables students to explore how to make quadrilaterals in various orientations on the grid. For each kind of quadrilaterals, 3 to 4 progressive questions are given to students. In each question, one or two sides of the quadrilateral are given and students could explore how to add lines to make the required quadrilateral by dragging the points in the applet.
After the exploration, teacher discusses with students the methods of making quadrilaterals with focus on how to make sides equal to, parallel to and perpendicular to the given sides, by looking at the grid they occupy.
[b]2) Learning Objective[/b]
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[*]Recognize the methods of making common quadrilaterals such as squares, rectangles, rhombuses, parallelograms and trapeziums in various orientations on the grid.
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[b]3) Teaching Approach[/b]
This applet provides a problem-solving environment in which a co-construction teaching approach is expected. Students first explore themselves how to construct the required quadrilaterals on the grid. Teachers then provide opportunities for students to explain their methods, and finally summarize with students collectively the general methods of making quadrilaterals.
[b]4) Teacher’s Note[/b]
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[*]In the beginning students can use the given ruler in the applet to determine right angles and lengths.
[*]Teacher then asks them to think about how to make and check equal, perpendicular and parallel sides without using the ruler. Students can click each line segment to see the grid it occupies, and use this to make equal, perpendicular and parallel sides.
[*]Some students may think, for example, that the diagonal of a rectangle of dimensions 2 cm × 1 cm is 2 cm (see Q.2(a)). In this case asks students to measure the diagonal using the ruler.
[*]After finishing all the questions, teachers can let students to make their own quadrilaterals by checking the “Reset” box. Note that sometimes students must use the ruler to determine what quadrilaterals they have made. For example, if some of them make a parallelogram of a horizontal side 5 cm, and a slanted side of run 3 cm and rise 4 cm, since they haven’t learnt Pythagoras Theorem yet, they have to use the ruler to measure that the slanted side is 5 cm and the parallelogram is in fact a rhombus.
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Anthony Or. Education Bureau, Hong Kong.
orchiming@gmail.com
