# What is Pi? Polygon approximation method.

- Author:
- Tibor Marcinek

The applet shows the old method used to approximate the value of π. Archimedes used a 96-sided polygons to find that the value of π is 223/71 < π < 22/7 (3.1408 < π < 3.1429). In 1630, an Austrian astronomer Christoph Grienberger found a 38-digit approximation by using 10^40-sided polygons. This is the most accurate approximation achieved by this method. In this activity, you will explore how the method works.
Use the slider n to change the number of sides of a regular polygon. Drag the point B to change he circle radius. Observe how the circle radius relates to the perimeter of inscribed and circumscribed regular polygons. Answer the questions on the worksheet.