# Constructive Triangles: Third Box

From wikisori

## Contents

### Age

6-9.

### Materials

Box 3 -

- Twelve blue right-angled scalene triangles with no black lines. The angles measure 30, 60, and 90 degrees.

### Preparation

### Presentation

- Isolate one triangle.
- Ask the child to identify each of the angles, and the biggest and smallest angles.
- This angle which is neither smallest nor biggest we can call the medium angle.
- The child names each angle: smallest angle, medium angle, biggest angle.
- First star: Let's unite all the triangles by their smallest angle.
- The directress positions a few and allows the child to continue.
- How many points does this star have? Twelve.
- With all of the triangles at our disposal, we can make only one star with twelve points.
- Second star: Let's unite all the triangles by the medium angles.
- How many points does this star have? Six.
- Try to make another star with the triangles that are left.
- With all the triangles at our disposal, we can make two stars with six points.
- Third star: Let's unite all of the triangles by the largest angle.
- How many points does this star have? Four.
- This symbol is very famous; it is the star of Saint Brigid, the patron saint of Ireland.
- Try to make another star like this.
- With all the triangles at our disposal, we can make three stars with four points.

### Control Of Error

### Points Of Interest

### Purpose

Use of the triangle as a constructor to indirectly demonstrate the following:

- 30
^{o}x 12 triangles = 360^{o} - 60
^{o}x 6 triangles = 360^{o} - 90
^{o}x 4 triangles = 360^{o} - 360
^{o}/ 30^{o}= 12 triangles - 360
^{o}/ 60^{o}= 6 triangles - 360
^{o}/ 90^{o}= 4 triangles - 360
^{o}/ 12 triangles = 30^{o} - 360
^{o}/ 6 triangles = 60^{o} - 360
^{o}/ 4 triangles = 90^{o}

### Variation

### Links