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Project Summary

Difficulty	8
Time required	Short (several days)
Prerequisites	Must understand the concept and method of a mathematical proof
Material Availability	Readily available (laptop computer helpful for live demonstration)
Cost	Very Low (under $20)
Safety	No issues

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Abstract

Objective

This project has two objectives:

1. write a mathematical proof for the construction of a circle inscribed in a triangle;
2. illustrate the proof with a dynamic figure created with the Geometry Applet.

Introduction

The illustration below shows a circle, with center at point D, inscribed within triangle ABC. By definition, an inscribed circle is tangent to the three sides of the triangle.

This project has two objectives:

1. write a mathematical proof for the construction of a circle inscribed in a triangle;
2. illustrate the proof with a dynamic figure created with the Geometry Applet.

What is the Geometry Applet? It is a very cool program written by Professor David Joyce to illustrate an online version of Euclid's Elements. The applet creates dynamic diagrams in which you can manipulate the geometric figures by clicking and dragging on points. You program the applet much like creating a geometrical construction by hand, so as the points are dragged, all of the essential relationships in the diagram remain intact. It is an engaging and intuitive way to illustrate the generality of your proof. To see an example of the Geometry Applet in action, see any of these three projects:
Throwing You Some Curves: Is Red or Blue Longer?
Thinking in (Semi-)Circles: The Area of the Arbelos
Chain Reaction: Inversion and the Pappus Chain Theorem

To learn how to use the Geometry Applet to create your own dynamic diagrams, see:
Getting Started with the Geometry Applet

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

• the concept of a tangent point,
• congruent triangles,
• bisection of an angle.

Bibliography

• The Math Forum at Drexel University has some good advice on how to build a mathematical proof:
  http://mathforum.org/library/drmath/view/54693.html
• There are many more examples in their FAQ section:
  http://mathforum.org/dr.math/faq/faq.proof.html
• For help with the programming the Geometry Applet, see:
  Getting Started with the Geometry Applet
• The Geometry Applet was kindly provided to Science Buddies by its author, Professor David Joyce, who wrote it for illustrating an amazing online edition of Euclid's Elements:
  http://aleph0.clarku.edu/~djoyce/java/elements/elements.html

Materials and Equipment

• For completing the proof manually, all you'll need is:
  • pencil,
  • paper,
  • compass, and
  • straightedge.
• For creating a dynamic diagram of the proof using the Geometry Applet, you will also need:
  • a computer,
  • a text editor (Notepad will work fine),
  • a Web browser program (e.g., Internet Explorer or Firefox).
• For a live demonstration along as part of your display, a laptop computer is recommended.

Experimental Procedure

1. Do your background research,
2. organize your known facts, and
3. spend some time thinking about the problem and you should be able to come up with the proof.

Variations

• Corollary: prove that the lines bisecting the three vertex angles of a triangle share a common intersection point.

• For more science project ideas in this area of science, see Computer Science Project Ideas.

Credits

Andrew Olson, Ph.D., Science Buddies

Last edit date: 2005-11-29 11:33:21

Career Focus

If you like this project, you might enjoy exploring careers in Computer Science.

	Computer Programmer Computers are essential tools in the modern world, handling everything from traffic control, car welding, movie animation, shipping, aircraft design, and social networking to book publishing, business management, music mixing, health care, agriculture, and online shopping. Computer programmers are the people who write the instructions that tell computers what to do.			Computer Software Engineer Are you interested in developing cool video game software for computers? Would you like to learn how to make software run faster and more reliably on different kinds of computers and operating systems? Do you like to apply your computer science skills to solve problems? If so, then you might be interested in the career of a computer software engineer.
	Network Systems and Data Communications Analyst Computers are an important part of our lives. We use computers to hold and process data, to control manufacturing factories, and to surf the Internet. We are all part of many different kinds of computer networks that are continually sharing information. The role of the network systems and data communications analyst is to design, model, and evaluate computer networks so that they can share information seamlessly. This is an exciting career for those people who enjoy working with rapidly changing technology.			Software Quality Assurance Engineer and Tester Software quality assurance engineers and testers oversee the quality of a piece of software's development over its entire life cycle. Their goal is to see to it that the final product meets the customer's requirements and expectations in both performance and value. During the software life cycle, they verify (officially state) that it is possible for the software to accomplish certain tasks. They detect problems that exist in the process of developing the software, or in the product itself. They try and make things not work (try to "break" the software) by creating errors or combinations of errors that a user might make. For example, if a user enters a period or a pound sign for a password, will that break the software? They seek to anticipate potential issues with the software before they become visible. At the end of the life cycle, they reflect upon how problems or bugs arose, and figure out ways to make the software development process better in the future.
	Computer Hardware Engineer Whether you are playing video games, surfing the Internet, or writing a term paper, computers are an integral part of our daily lives. Computer hardware engineers work to make computers faster, more robust, and more cost-effective. They design the microprocessor chips that make your computer function, along with the equipment that makes computing easy and fun to do.

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