 Manipulative 1: Perimeter of a polygon. Created with GeoGebra. 

The perimeter of a
polygon,
is the edges, or boundary of the polygon, or the length of those edges. The
perimeter of a simple closed curve is the boundary
of that curve or the length of the boundary. The perimeter of a circle is called
a circumference.
Click on the blue points in manipulative
1 and drag them to change the figure. The perimeter is the black lines of the polygon.
The length of the perimeter is displayed in the figure. Manipulative 2 shows the
perimeter of an ellipse. As you drag the points in manipulative 2, note that if the
figure becomes a hyperbola, the perimeter is undefined. This is because a hyperbola is
not a simple, close curve.

 Manipulative 2: Perimeter of an ellipse. Created with GeoGebra. 
