Triangle Explorer Lesson Plan

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Abstract

Students learn how to calculate the area of triangles using a variety of materials including computer applets.

Standards (NCTM 3-5)

Measurement

Understand measurable attributes of objects and the units, systems, and processes of measurement

• Understand such attributes as length, area, weight, volume, and size of angle and select the appropriate type of unit for measuring each attribute
• Understand the need for measuring with standard units and become familiar with standard units in the customary and metric systems.

Apply appropriate techniques, tools, and formulas to determine measurements

• Develop strategies for estimating the perimeters, areas, and volumes of irregular shapes.
• select and apply appropriate standard units and tools to measure length, area, volume, weight, time, temperature, and the size of angles.

Student Prerequisites

• 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.
• students will need pencil, paper, and rulers.

Lesson Outline

1. Focus and Review
• Review any pertinent vocabulary.
• Tell the students that today they will be learning about area.
2. Objectives
Students will calculate the area of different triangles using a variety of methods.


3. Guided Practice
• Have all the students cut out a square. Do not specify the size. (You may want to remind the students that the corners of a square are right angles.)
• Once the students have completed their squares, have them measure the area of their square.
• Have the students crease their square from the lower left corner to the upper right corner and cut along the crease to create two right triangles with equal areas.
• Ask the students if anyone can tell the class the area of one or both of the triangles.
• Have that student explain to the class how he/she knew the area of the triangle.

4. Teacher Input
• Remind the students that what they have been measuring is called area.
• Remind the students that area is measured in square units. These units can be square m, cm, in, ft, etc.
• Ask the class to come up with a formula to calculate the area of right triangles.
• Tell them that they need to be able to explain why their equation should work for all right triangles.
• If no one mentions the length * width / 2 method, mention the method to the class and have them try it.
• Show the students how to operate the Triangle Explorer Applet.

5. Independent Practice
• Have the students work in pairs to explore the Triangle Explorer Applet.
• Instruct the students to work 5 easy problems, 5 medium problems, and 5 hard problems.
• If you need to have something to check, have the students draw the computer generated shapes on a sheet of graph paper and write the areas beside the shapes.

6. Closure
• Clarify how to calculate the area of a right triangle and ask if there are any questions.
• Discuss the different ways the students used to calculate the areas of more difficult triangles.

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