﻿ Parallel Lines, a Transversal and the angles formed. Corresponding, alternate exterior, same side interior...
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# Parallel Lines cut by a Transversal

## Angles formed

#### What is a transversal?

Answer: A transversal is a line, like the red one below, that intersects two other lines.

Typically, the intercepted lines like line a and line b shown above above are parallel, but they do not have to be.

#### What is so special about a transversal?

Answer: When a transversal cuts (or intersects) parallel lines several pairs of congruent and supplementary angles are formed.

### Interior and Exterior Regions

We divide the areas created by the parallel lines into an interior area and the exterior ones.
Interior
Exterior
These regions are used in the names of the angle pairs shown next.

### The Congruent Angle Pairs

There are 3 types of angles that are congruent: Alternate Interior, Alternate Exterior and Corresponding Angles.

#### Can you make a Z?

A way to help identify the alternate interior angles.

Some people find it helpful to use the 'Z test' for alternate interior angles.
If you can draw a Z or a 'Backwards Z' , then the alternate interior angles are the ones that are in the corners of the Z

##### Problem 1

$$\angle$$D and $$\angle$$W
$$\angle$$X and $$\angle$$C

##### Problem 2

$$\angle$$A and $$\angle$$Z
$$\angle$$Y and $$\angle$$B

##### Problem 3

$$\angle$$A and $$\angle$$W
$$\angle$$D and $$\angle$$Z
$$\angle$$X and $$\angle$$B
$$\angle$$C and $$\angle$$Y

### The Supplementary Angle Pairs

There are 2 types of supplementary angles that are formed: same side interior and same side exterior.

Same Side Interior
Same Side Exterior

### Interactive Parallel Line and Angles

 ∠GEH ∠EFI 90 90 90 90 90 90 90 90
Drag the triangle points to change the angles