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Geometry for Elementary School/Copying an angle
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Copying a triangle Copying an angle Constructing a triangle
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
Draw a line between A and C and get .
Copy the triangle and get
Claim
The angles and are equal.
Proof
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.
it:Geometria per scuola elementare/Copiare un angolo