8th grade Instructional Unit

Unit 2 – Exponents & Square Roots Review
Unit 3 – Pythagorean Theorem Instructional Unit

by
Nancy Perzel

Day 2 - Triangles

Warm-Up:

Ask the students to brainstorm all of the vocabulary terms they can think of that can describe triangles.  (Supplemental resource: Interactive Dictionary) Review these terms as a class.

 

Activity 1:

To incorporate technology and give students a chance to work in groups (2-4 students) you could have them create flipcharts or a GSP document to specify the properties and characteristics of each type of triangle.  (Isosceles, scalene, equilateral, acute, obtuse, right) 

Example flipchart page on Right Triangles that shows a drawing (visual aid) along with important vocabulary terms and unique properties.

Instructions on how to construct a right triangle on GSP.

Another option for whole-group instruction would be to take out Geoboards during this portion of the lesson and construct the triangles as a class and discuss their properties together.

 

Activity 2:

Focus on Right Triangles

This can be done using a physical (5x5) geoboard, dot/graph paper, GSP, or using an Interactive Geoboard found on the website for the National Library of Virtual Manipulatives (http://nlvm.usu.edu/en/nav/vlibrary.html).

 

1) Using one rubber band, make a rectangle on your geoboard. What is the area?   Using a second rubber band create a diagonal for the rectangle?  What two shapes are formed?  What are the areas of the new shapes youÕve created?  Why?

2) Find the right triangle with the smallest area on your geoboard. What is the area?

 

3) Find the right triangle with the next smallest area on your geoboard. What is the area? 

 

4) Find the right triangle with the largest area on your geoboard.  What is the area?

 

5) How many different right triangles can you make? (A: total of 17) 

 

*Not the best quality, but here is a picture of all possible constructions:

 

 

 

For extended activities, visit the following website:

 

http://mathforum.org/trscavo/geoboards/geobd6.html

Additional Technology Resources:

-       http://www.brainpop.com/math/geometryandmeasurement/typesoftriangles/preview.weml

   

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