#### 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.

### 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?

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*

#### Can you identify each type of congruent

angle in the picture below?

**Alternate Interior Angles**

$$\angle $$ 3 and $$\angle $$ 6

$$\angle $$ 4 and $$\angle $$ 5

**Alternate Exterior Angles**

$$\angle $$ 2 and $$\angle $$ 7

$$\angle $$ 1 and $$\angle $$ 8

**Alternate Interior Angles**

$$\angle $$ 1 and $$\angle $$ 5

$$\angle $$ 4 and $$\angle $$ 8

$$\angle $$ 2 and $$\angle $$ 6

$$\angle $$ 3 and $$\angle $$ 7

#### Line P is parallel to line v

**Alternate Interior Angles**

$$ \angle$$D and $$ \angle$$W

$$ \angle$$X and $$ \angle$$C

**Alternate Exterior Angles**

$$ \angle$$A and $$ \angle$$Z

$$ \angle$$Y and $$ \angle$$B

**Identify the corresponding angles**

$$ \angle$$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

Click and Drag Points E and F to explore the relationship of corresponding, alternate interior and alternate exterior angles that are formed by a transversal and parallel lines. (Full Size Version)