1. 1 2 1 2 PROPERTIES OF PARALLEL LINES POSTULATE
POSTULATE 15 Corresponding Angles Postulate
If two parallel lines are cut by a transversal, then the pairs of corresponding angles are congruent. 1 2

2. Do you remember??? 3 4 PROPERTIES OF PARALLEL LINES
THEOREMS ABOUT PARALLEL LINES
THEOREM 3.4 Alternate Interior Angles
If two parallel lines are cut by a transversal, then the pairs of alternate interior angles are congruent.
Do you remember??? 3 4

3. 3 4 3 4 PROPERTIES OF PARALLEL LINES THEOREMS ABOUT PARALLEL LINES
THEOREM 3.8 Alternate Interior Angles Converse
THEOREM 3.4 Alternate Interior Angles
If two parallel lines are cut by a transversal, then the pairs of alternate interior angles are congruent.
If two parallel lines are cut by a transversal so that alternate interior angles are
congruent, then the lines are parallel. 3 4
3 4

4. Do you remember??? 5 6 PROPERTIES OF PARALLEL LINES
THEOREMS ABOUT PARALLEL LINES
THEOREM 3.5 Consecutive Interior Angles
If two parallel lines are cut by a transversal, then the pairs of consecutive interior angles are supplementary.
Do you remember??? 5 6

5. Do you remember??? 5 6 m5 + m6 = 180 ° PROPERTIES OF PARALLEL LINES
THEOREMS ABOUT PARALLEL LINES
THEOREM 3.9 Consecutive Interior Angles Converse
THEOREM 3.5 Consecutive Interior Angles
If two parallel lines are cut by a transversal, then the pairs of consecutive interior angles are supplementary.
If two parallel lines are cut by a transversal so that consecutive interior angles are supplementary, then the lines are parallel.
If two parallel lines are cut by a transversal, then the pairs of consecutive interior angles are supplementary.
If two parallel lines are cut by a transversal, then the pairs of consecutive interior angles are supplementary.
If two parallel lines are cut by a transversal, so that consecutive interior angles are supplementary, then the lines are parallel.
Do you remember??? 5 6
m5 + m6 = 180 °

6. Do you remember??? 7 8 PROPERTIES OF PARALLEL LINES
THEOREMS ABOUT PARALLEL LINES
THEOREM 3.6 Alternate Exterior Angles
If two parallel lines are cut by a transversal, then the pairs of alternate exterior angles are congruent.
Do you remember??? 7 8

7. 7 8 7 8 PROPERTIES OF PARALLEL LINES THEOREMS ABOUT PARALLEL LINES
THEOREM Alternate Exterior Angles Converse
THEOREM 3.6 Alternate Exterior Angles
If two parallel lines are cut by a transversal, then the pairs of alternate exterior angles are congruent.
If two parallel lines are cut by a transversal so that alternate exterior angles are congruent, then the lines are parallel. 7 8
7 8