# Constructive Triangles: Second Box: Trapezoid

From wikisori

## Contents

### Age

6-9.

### Materials

Box 2 -

- Two blue equilateral triangles
- Two blue right-angled isosceles triangles
- Two blue right-angled scalene triangles
- One blue obtuse-angled scalene triangle
- One blue right-angled scalene triangle (corresponds to the red triangle from Box 1)

### Preparation

### Presentation

- With the two small red triangles, invite the child to unite the triangles along the black lines and identify the figure obtained - a trapezoid.
- Using the two corresponding blue triangles, invite the child to form the figure which he already knows and to identify it - a trapezoid.
- Continue making other quadrilaterals using only the obverse sides.
- The directress identifies the figure obtained.
- Since it has four sides we can call it a quadrilateral.
- It is a concave quadrilateral - a boomerang (it may also be called a re-entrant).
- Invite the child to turn over one triangle to form any other figures, quadrilaterals or triangles.
- The quadrilateral is called a common quadrilateral.
- The triangle is an obtuse-angled isosceles triangle.
- Note: This triangle has great importance in the later study of the area of a trapezoid.
- Recall the figures formed by these triangles; there are four.

### Control Of Error

### Points Of Interest

### Purpose

- Exploration of the triangle as the constructor of triangles and quadrilaterals.

### Variation

### Links

Constructive Triangles Boxes # 1-5

### Handouts/Attachments