PARALLEL LINES AND TRANSVERSALS

CORRESPONDING ANGLES POSTULATE

• Two lines cut by a transversal are parallel if and only if the pairs of corresponding angles are congruent.

ALTERNATE INTERIOR ANGLES THEOREM

• Two lines cut by a transversal are parallel if and only if the pairs of alternate interior angles are congruent.

ALTERNATE EXTERIOR ANGLES THEOREM

• Two lines but by a transversal are parallel if and only if the pairs of alternate exterior angles are congruent.

CONSECUTIVE INTERIOR ANGLES THEOREM

• Two lines cut by a transversal are parallel if and only if the pairs of consecutive interior angles are supplementary.

CONSECUTIVE EXTERIOR ANGLES THEOREM

• Two lines cut by a transversal are parallel if and only if the pairs of consecutive exterior angles are supplementary.

EXAMPLE

• Find each numbered angle.

EXAMPLE

• Find the value of x.

EXAMPLE

• Find the value of x. The picture may not be drawn to scale.

(3x + 5)o

(7x – 15)o

TRANSITIVE PROPERTY OF PARALLEL LINES

• If two lines are parallel to the same line, then they are parallel to each other.

ASSIGNMENT

• Pg. 157 #4-8 all, 27-35 odds• Pg. 165 #3-8 all