Transcript 3.2 Properties of Parallel Lines • Corresponding Angles Postulate – Postulate 3.1 – If a transversal intersects two parallel lines, then corresponding angles.

3.2 Properties of Parallel Lines
• Corresponding Angles Postulate – Postulate 3.1
– If a transversal intersects two parallel lines, then
corresponding angles are CONGRUENT!!
1  5
 2  6
3  7
 4  8
Identifying Congruent Angles
• Which angles measure 55? How do you know?
• The measure of angle 7 = 55° - Corresponding Angles
Postulate.
• The measure of angle 1 = 55° - Vertical Angles Theorem.
• The measure of angle 5 = 55° - Corresponding Angles
Postulate because angle 1 and angle 5 are corresponding
angles.
Alternate Interior Angles Theorem
• If a transversal intersects two parallel lines,
then alternate interior angles are congruent.
3  5
 4  6
Same-Side Interior Angles Theorem
• If a transversal intersects two parallel lines,
then same-side interior angles are
supplementary.
m4  m5  180
m3  m6  180
Alternate Exterior Angles Theorem
• If a transversal intersects two parallel lines,
then alternate exterior angles are congruent.
1  7
2  8
Finding Measures of Angles
• What are the measures of the missing angles?
m3  105
m4  105  180
m4  75
Finding an Angle Measure
• What is the value of y?
( y  40)  80  180
y  120  180
y  60
More Practice!!!!!
• Homework – Textbook p. 153 - 154 #7 –
20 all!