# Geometry for Elementary School/Copying an angle

In this chapter, we will show how to copy an angle to other angle .
The construction is based on Book I, proposition 23.

## The construction

edit- Draw a line between
**A**and**C**and get . - Copy the triangle and get

## Claim

editThe angles and are equal.

## Proof

edit- The triangles and congruence.
- Therefore the angles of the triangles equal.
- Hence, and are equal.

Note that any two points on the rays can be used to create a triangle.