# Dragging Test

The main feature of dynamic (or interactive) geometry is that you should be able change a geometrical object without changing the significant properties of the object. In the applet above, you can change the shapes but they are always a rectangle, rhombus, parallelogram and trapezium.

If you draw a rectangle on a paper, your rectangle is merely **one**
example of a rectangle. If you draw a rectangle in GeoGebra by placing four
points, you can destroy the rectangle by dragging one of these points.

If you want to make a rectangle as a construction, you must consider the significant
properties of a rectangle. When the construction is done, you should be able
to drag some of the vertices to change the rectangle without destroying the
properties of the rectangle; your construction should pass the **dragging
test**.

## Rectangles and parallelograms

The tools Perpendicular Line and Parallel Line can be used to construct rectangles and parallelograms respectively. Make sure that you know how to use these tools.

## Exercise 1 - Parallel and perpendicular

Make sure you know how to construct a line through a point parallel to a given line ( a line already present in the construction).

Make sure you know how to construct a line through a point perpendicular to a given line.

Make sure you know how to construct a line through a point perpendicular to
a given line if the **point is on the line**, as in the picture
to the right.

## Exercise 2 - Rectangle

Make a rectangle as a construction. When the construction is done, you should be able to move the points to change the size and the appearance; the quadrilateral should still remain a rectangle when moving the points.

## Exercise 3 - Parallelogram

Make a parallelogram as a construction. When the construction is done, you should be able to move to points to change the size and the appearance; the quadrilateral should still remain a parallelogram when moving the points.

# further info:

software: List of interactive geometry software

some examples, not GeoGebra: http://www.gogeometry.com/geometry/dynamic_geometry.html

by Malin Christersson under a Creative Commons Attribution-Noncommercial-Share Alike 2.5 Sweden License