You need to install ActiveX plug-in to be able to view this model.
The model illustrates the conditions whose satisfaction provides to inscribe a circle into a quadrilateral or to circumscribe the first about the second.
A quadrilateral can be specified by a figure which provides its changing by the Mouse. In so doing, the numerical values of all sides and angles of a quadrilateral, and also the sums of its opposite angles and sides, are displayed.
To show the diagonals of a rectangle tick off the corresponding window.
If you think it is possible to inscribe a circle into the rectangle (or to circumscribe that about it), choose the respective option. The model will make constructing or give the message of the failure to do so for that quadrilateral.
Notice that in order for a circle should be inscribed into or circumscribed about any quadrilateral, it is necessary to satisfy the defined relations between the values of its angles or between the lengths of its sides.
You can download it here.