# Construction of a triangle with two angles and included side

From Karnataka Open Educational Resources

Construction of a triangle when two angles of a triangle and a side are known and understanding the side given can only be constructed between the two angles to form a unique triangle. Construction follows ASA congruence rule.

## Contents

### Objectives

- To construct a triangle given two sides and an angles
- To understand the given angle should be included angle when two sides are given

### Estimated Time

20 minutes

### Prerequisites/Instructions, prior preparations, if any

Prior understanding of point, lines and angles, elements of triangle, properties of triangle

### Materials/ Resources needed

- Digital : Computer, geogebra application, projector.
- Non digital : Worksheet and pencil
- Geogebra files : “Triangle construction (1side-2angles)”

Download this geogebra file from this link.

### Process (How to do the activity)

- For given 2 angles, if the angles add to 180o, can you construct the triangle?
- Is it possible to construct a triangle with only 2 given angles. What is the other parameter required for construction.
- If any one side is specified, along with 2 angles how many triangles are possible.
- If the side given is an included side, how many triangles are possible.

**Evaluation at the end of the activity**

- Why should the given side be included side?
- For the given A, A and S are the triangles AAS, ASA and SAA congruent triangles.