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Geometry Science Fair Project

Approximating Pi with Polygons and Algebra

Hard
Approximating Pi with Polygons and Algebra | Science Fair Projects | STEM Projects
Can you pin down the value of pi by wrapping polygons tighter and tighter around a circle? You start with a square drawn around a circle of radius 1. Then you double the number of sides to 8, then 16, and so on. Each polygon's perimeter gets closer to the circle's circumference. This process produces a recursive equation that approaches pi from above. The project also shows that this upper-bound formula matches a famous expression published by Francois Viete centuries ago. Finally you derive an algebraic polynomial where one root is pi itself. The other roots are new numbers called the Pi Associates, whose properties remain unexplored.

Hypothesis

The hypothesis is that Pi can be derived from an Algebraic Polynomial.

Science Concepts Learned

Pi

Pi is the number you get when you divide any circle's edge length by its width. One way to close in on that ratio is to wrap polygons tighter and tighter around a circle. You start with a square, then double the sides to 8, then 16, and so on. Each polygon's perimeter gets closer to the circle's circumference, producing a value that approaches pi from above.

Polygons

A polygon with more sides hugs a circle more tightly — each added straight segment brings the flat outline closer to a curve. When you wrap a square around a circle of radius 1 and double its sides to 8, then 16, the perimeter shrinks toward the circle's circumference. That shrinking value approaches pi from above, producing a recursive equation that matches a famous expression published by François Viète centuries ago.

Circumference

The circumference of a circle can be approached step by step using polygons. In this project, you draw regular polygons around a circle of radius 1 and keep doubling the number of sides. Each polygon's perimeter gets closer to the circle's circumference, showing that the distance around a circle is a fixed value that polygons can approximate but never quite match.

Recursive Sequences

Recursive sequences are patterns where each new number is built from the ones before it. This experiment puts that idea to work: you start with a square drawn around a circle of radius 1, then double the number of sides to 8, then 16, and so on. Each polygon's perimeter feeds the next calculation, with every step creeping closer to pi from above. As the sides multiply, the upper-bound expression converges — and it turns out to match a famous formula published by François Viète centuries ago. Finally, you derive an algebraic polynomial whose roots include pi itself, along with new numbers called the Pi Associates.

Geometric Convergence

Wrapping polygons around a circle reveals geometric convergence in action. You start with a square drawn around a circle of radius 1, then double the sides to 8, then 16, and beyond. As the side count grows, each polygon's perimeter closes in on the circle's circumference. This process produces a recursive equation that approaches pi from above — and it turns out to match a famous upper-bound formula published by François Viète centuries ago. From there, you derive an algebraic polynomial where one root is pi itself, with the remaining roots being new numbers called the Pi Associates, whose properties remain unexplored.

Inscribed and Circumscribed Figures

Drawing shapes around a circle gives an upper estimate of its size. You start with a square drawn around a circle of radius 1, then double the number of sides to 8, then 16, and so on. As each polygon gains more sides, its perimeter drops closer to the true circumference. This process produces a recursive equation that approaches pi from above — and it turns out to match a famous upper-bound expression published by Francois Viete centuries ago.

Method & Materials

You will use regular circumscribed polygons about circle of radius 1 to derive an upperbound expression for Pi. You will start from a square and construct an 8-sided regular polygon, doubling the number of sides. This procedure can be repeated endlessly doubling the sides of the polygon with every step.
You will need regular polygons, a circle of radius 1, and a calculator.

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Results

Through this project, we have discovered the upperbound recursive equation for Pi and the Pi Associates. We have also shown that François Viete's expression for Pi is equivalent to my last year's lowerbound expression for Pi.

Why do this project?

This science project is so interesting and unique because it involves discovering the mystery of Pi and the Pi Associates.

Also Consider

Experiment variations to consider include using different shapes of polygons and different radii of circles.

Full project details

Additional information and source material for this project are available below.
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