Download Section 3-1 Parallel Lines and Planes

Warm - Up
• Go over any problems that you got wrong
on the test with your seat partner 
Parallel Lines and Planes
Chapter 3
Definitions
• Parallel lines
–Algebra 1 review: two lines that
have the same slope
–Geometry application: two
coplanar lines that do not
intersect
If the are not parallel…
• Two other options
– Intersecting
– Skew
• Definition: lines that are not
coplanar
• Note: skew lines are neither
parallel nor intersecting.
Can you find an example of skew
lines in the classroom?
Parallel Planes
• Definition: planes that do not
intersect
–Such as…
Note: all planes are either
parallel or intersecting
Sometimes, Always, Never
1. Two lines in the same plane are ____
parallel.
2. Two lines in the same plane are __
skew.
3. Two noncoplanar lines ____
intersect.
4. Two planes ____ intersect.
5. If two planes do not intersect, then
they are ______ parallel.
Answers
1. Two lines in the same plane are S
parallel.
2. Two lines in the same plane are N
skew.
3. Two noncoplanar lines N intersect.
4. Two planes S intersect.
5. If two planes do not intersect, then
they are A parallel.
Theorem– Parallel lines of
intersection.
• If 2 parallel planes are cut by a third plane,
then the lines of intersection are parallel.
• Show me examples in the classroom!
Transversal
• A line that intersects lines in different
points.
Practice!!
Do #1-6 of the practice alone!!
• True or False
• Name the Transversal
Describing Angles
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Exterior angles
Interior angles
Alternate interior angles
Alternate exterior angles
Same-side interior angles
Same-side exterior angles
Corresponding angles
Practice!!
• What angles are formed when two
lines are cut by a transversal?
With Your Partner
Name the 2 lines and the
transversal that form each pair
of angles.
More Practice!
• Do classroom exercises on pg 75 with a
group of 3 or 4.
Homework
• Mini-Quiz on 3.1 Tomorrow
• Pg. 76-77 #1-17, 30-39 ODD