Every point in the first quadrant of {width,height plane} corresponds to a rectangle.
The applet allows you to generate either a family of rectangles by moving the GOLD point along a height = constant/width curve or a family of rectangles by moving a GOLD point along a height+width = constant curve.
[You can position each of these curves by dragging the small WHITE dots.]
Can you explain the nature of the curves generated in the {Perimeter, Area} plane as you drag the GOLD dots in the {width, height} plane?
qualitatively? analytically?
What questions would/could you put to your students based on this applet?
What have you learned from this applet?