# Interactive Calculate Tau (6.28...)

This interactive demonstrates how the geometric constant Tau (τ) can be approximated using two polygons. One polygon is inscribed in the circle, the other is cricumscribed around the circle. Then using the perimeter of the two polygons a lower-bound and upper-bound approximation can be calculated. This is because τ is defined geometrically as the length of any circle’s circumference dvided by the length of its radius.

The number PI(π) is defined as the length of any circle’s circumference divided by its diameter:

To approximate π, we can use the perimeter of a **n** sided polygon to represent the circumference of the circle. As the number of sides increase, the approximation becomes more accurate.