(Updated on 29 Jan 2012)
To see how a quadrilateral could be dissected into a rectangle by a line joining the mid-points of one pair of opposite sides, and the perpendiculars to this line from the mid-points of the other pair of opposite sides.
This could be an introduction to the problem of dissecting a triangle into a rectangle or a square (Dudeney's Puzzle). See "Cut Triangles into Rectangles & Dudeney's Puzzle Generalized" (http://www.geogebratube.org/material/show/id/3589 ).
Anthony Or. Education Bureau, Hong Kong. (orchiming@gmail.com)
Dissecting Quadrilaterals
