Special Angles on Parallel Lines

Transversal

A line intersecting two or more other lines in the plane.

How many angles are

created by the transversal in this picture?

Corresponding Angles

Angles that lie in the same position on opposite lines

hg

fe

dc

ba

and a e

Alternate Interior Angles

Angles that lie in between 2 lines on opposite sides of the transversal.

hg

fe

dc

ba

and c f

Alternate Exterior Angles

Angles that lie outside of the 2

lines on opposite sides of the transversal

hg

fe

dc

ba

and a h

Consecutive Interior Angles

Angles that lie in between two lines

that are on the same side of the

transversal hg

fe

dc

ba

and c e

Let’s look deeper at those angles

• Open 3.2 Angles on Parallel Lines Investigation on scevmath.org and geogebra.

• Work through the investigation. Fill in the blanks, answer question 8 on your desk and be sure to answer the last question on a piece of paper to be handed in (finding the missing angle measures).

ConjecturesIf two parallel lines are cut by a

transversal, then corresponding angles are congruent.

If two parallel lines are cut by a transversal, then alternate interior angles are congruent.

If two parallel lines are cut by a transversal, then alternate exterior angles are congruent.

Conjectures continued…

If two parallel lines are cut by a transversal, then consecutive interior angles are supplementary.

Which Pair is Which?

ponm l

kji

hgfe dcba

1) Name an angle that is an Alternate Interior Angle with angle g.

2) Name a pair of angles that are supplementary and tell me WHY you know that.

3) If k = 108 degrees, find j and f

4) If d = 34 degrees, find g and f.