Pi Day 2018

Happy Pi Day 2013, this interactive activity will guide you through ways to find π using polygons.

Most people know the definition of PI as the ratio of the circumference of a circle to its diameter. They have probably used PI in circle problems, calculating the area using area = πr2 or the circumference using C = 2πr or C = πd . But what of this mysterious number, is it possible to create a visual analogy. This demonstration attempts to do so by examining and manipulating a regular polygon.

This will be done in two ways firstly by considering the perimeter of a regular polygon which fits perfectly in a circle of radius one, the polygon can be opened to form a straight line and its perimeter then measured. To show how π relates to area we again use a polygon, dividing its area into triangles.

The controls

For the sake of consistency with the other activites the controls are described below. But the best way to use this activity is to follow the instructions guide in the top right hand corner

Related Activities

If you like visual mathematics why not check out the interactive multiplication tables The inspiration for this activity actually came from playing around with the interactive fractal after setting the branches to one. The interactive polygon explorer. is better for teaching the various properties and angles of polygons.

Exterior angle of the polygon.
Control the Length of each side
Control the number of sides the polygon.
Length and angle are calculated for a regular polygon inside the circle
Animate close the polygon
Animate open the polygon
Toggle display of the exterior angles
Toggle to display triangles inside polygon
Select zoom area
Instruction use the buttons below for next and previous
Next Instruction
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