Introduction to Fractals:
Geometric Fractals

Abstract

This activity is designed to further the work of the Infinity, Self-Similarity and Recursion lesson by showing students other classical fractals, the Sierpinski Triangle and Carpet, this time involving iterating with a plane figure.

Objectives

Upon completion of this lesson, students will have:

• seen the classic geometric fractals
• reinforced their sense of infinity, self-similarity, and recursion
• practiced their fraction, pattern recognition, perimeter, and area skills

Activities

This lesson furthers students' knowledge of fractals through the following activities:

• Sierpinski Triangle
• Sierpinski Carpet

Standards

The activities and discussions in this lesson address the following Standards:

• Number sense, number operations, and number relationships
• Patterns, relationships and functions
• Geometry

Key Terms

This lesson introduces students to the following terms through the included discussions:

• fractal
• self-similarity
• infinity
• recursion
• iteration

Student Prerequisites

• Geometric: Students must be able to:
  • recognize and sketch objects such as lines, rectangles, triangles, and squares
  • understand the concepts of and use formulas for area and perimeter
• Arithmetic: Students must be able to:
  • build fractions from ratios of sizes
  • manipulate fractions in sums and products
• Technological: Students must be able to:
  • perform basic mouse manipulations such as point, click and drag
  • use a browser such as Netscape for experimenting with the activities

Teacher Preparation

Students will need:

• access to a browser
• pencil and graph paper
• copies of supplemental materials for the activities:
  • Sierpinski's Triangle Worksheet
  • Sierpinski's Carpet Worksheet

Lesson Outline

Groups of 2 or 3 work best for these activities; larger groups get cumbersome. Working through one or two iterations of each curve as a class before setting the groups to work individually can cut down on the time the students need to discover the patterns. Plan on 15-20 minutes for each exploration. The discussion below assumes that the student has worked with the activities from the Infinity, Self-Similarity, and Recursion lesson.

1. Have students run several steps of the Sierpinski Triangle. The students should look at the patterns made by the areas of the individual triangles and the total area. It may take drawing two or three iterations before the number pattern becomes obvious.

2. Repeat the previous exercise for the Sierpinski Carpet.

3. Lead a class discussion to make note of how these are similar to the line bender fractals from the Infinity, Self-Similarity, and Recursion lesson.

Alternate Outlines

This lesson can be rearranged in several ways.

• Combine these activities with those in the Infinity, Self-Similarity, and Recursion lesson.
• Omit the concept discussion and focus on pattern recognition and fractions.

Extensions

After these discussions and activities, the students will have seen a few of the classic plane figure fractals to compare with those from the Infinity, Self-Similarity and Recursion lesson. The next lesson, Fractals and the Chaos Game, continues the students' exploration of fractals by showing how other, seemingly different ideas can generate the same kinds of fractals.