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.