Applications of Parallelism

Mathematics — Second Preparatory

The transversal and the angles it forms

A line that cuts two other lines is called a transversal.
At each intersection four angles are formed.
When the transversal cuts two parallel lines, eight angles are formed, with the following relations:

Type of angles	Description	Relation
Corresponding	Two angles on the same side of the transversal one above each line	Equal
Alternate	Two inner angles on opposite sides of the transversal	Equal
Co-interior (same side)	Two inner angles on the same side of the transversal	Sum to 180°

Vertically opposite angles are always equal. If we know one angle at one intersection
we can find all eight angles.

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