TURTLE GEOMETRY MICROWORLD 3

In this appendix to the Geometry Microworld Part II Chris Gregory, Senior Lecturer in Mathematics at Bradford and llkley Community College, looks at the rectangle.

We have already come across the procedures SQUARE and TRI, which draw squares and equilateral triangles, in particular with the variable SIDE which allows us to make the shapes any size we like. These ideas can now be adapted to draw rectangles.

• Draw a Rectangle
Knowing already how to draw a square, how can we instruct the Turtle to draw any rectangle? Leave the children to discuss this - they will certainly have to consider carefully what, in general, rectangles look like and, in their procedures, which numbers will have to vary and which will remain constant.

This activity may well lead to children deciding that SQUARE is just a special case of RECT - that a square can be considered to be just a special kind of rectangles.

• Different Rectangles, Perimeters and Areas
Using the RECT procedure, make the Turtle draw rectangles which have all the same perimeter, say, 36 units. In other words, it has to travel the same distance each time.

The 'standard' procedure for drawing a rectangle is:

TO RECT :SIDE1 :SIDE2 FD :SIDE1 RT 90 FD :SIDE2 RT 90 FD :SIDE1 RT 90 FD :SIDE2 RT 90 END

Or, more neatly:

TO RECT :SIDE1 :SIDE2 REPEAT 2 [FD :SIDE1 RT 90                 FD :SIDE2 RT90] END

These procedures can be called by specifying two values, for the length and width of the rectangle:

e.g. RECT 15 20