### Area and Perimeter of Regular Polygons

*Triangle*

**Content Objective:**

Students will rediscover the method of finding
the perimeter and area of regular triangles.

**Materials:**

Rulers for pairs, triangle
perimeter worksheet, triangle area worksheet

**Procedure:**

### Perimeter

1. Collectively recall the definition of perimeter
given on review day. Have students get into pairs and distribute
perimeter worksheet. Once worksheet is complete and students have
compared their answers, ask the class as a whole the following
questions:

What do you notice about the side lengths
of our triangles?

What happens to the perimeter when the side
lengths are changed?

Is there a way to find the perimeter of a
regular triangle without measuring all three sides?

2. Demonstrate using Geometer's Sketchpad the
properties of the side lengths of regular triangles. Click here to use the GSP file and animate
the triangle.

### Area

1. Collectively recall the definition of area
given on review day. Now, have students get back into pairs and
distribute area worksheet. Once worksheet is complete and students
have compared their answers, ask the class as a whole the following
questions:

What do you notice about the base of our triangles?
Is there only one side of our triangles that can be considered
a base?

What happens to the area when the base lengths
are changed? What happens to the area when the altitude length
is changed?

How is length of the altitude related to the
length of the base?

Is there a way to find the area of a regular
triangle with one side length and the altitude length?

2. Demonstrate using Geometer's Sketchpad the
properties of the base and altitude of regular triangles. Click
here to use the GSP file and animate
the triangle.

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