Transcript Notes Section 3.1

Geometry Notes
Sections 3-1
What you’ll learn
How to identify the relationships between
two lines or two planes
 How to name angles formed by a pair of
lines and a transversal
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Vocabulary
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Parallel lines
Parallel planes
Skew lines
Transversal
Interior Angles
Exterior Angles
Consecutive (same – side ) Interior Angles
Alternate Interior Angles
Alternate Exterior Angles
Corresponding Angles
RELATIONSHIPS BETWEEN LINES
Coplanar
2 Lines are either
Noncoplanar
The lines intersect once
(INTERSECTING LINES)
The lines never intersect
(PARALLEL LINES)
The lines intersect at all pts
(COINCIDENT LINES)
Two noncoplanar
lines that never
intersect are called
SKEW lines.
This is what
we’ll study in
Chapter 3
Let’s start with any 2 coplanar lines
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2
1
3
4
5 6
7 8
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4 Interior Angles
3, 4, 5, 6
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Any line that
intersects two
coplanar lines at
two different points
is called a
transversal
8 angles are created
by two lines and a
transversal
4 Exterior Angles
1, 2, 7, 8
Consecutive Interior Angles
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2
1
3
4
5 6
7 8
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We have two pairs
of interior angles
on the same side of
the transversal
called Consecutive
Interior Angles or
same-side interior
angles
The two pairs of consecutive (same-side) interior:
3 &5 and 4 & 6
Alternate Interior Angles
2
1
3
4
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We have two
pairs of interior
angle on opposite
sides of the
transversal called
Alternate Interior
Angles
5 6
7 8
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The two pairs of alternate interior angles are:
3 &6 and 4 & 5
Alternate Exterior Angles
2
1
3
4
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We have two
pairs of exterior
angles on
opposite sides of
the transversal
called Alternate
Exterior Angles
5 6
7 8
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The two pairs of Alternate Exterior Angles
1 & 8 and 7 & 2
Corresponding Angles
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2
1
3
4
Corresponding
Angles are in the
same relative
position
5 6
7 8
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There are four pairs of Corresponding Angles
1 & 5, 2 & 6, 3 & 7, and 4 & 8
Find an example of each term.
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Corresponding
angles
Alternate exterior
angles
Linear pair of
angles
Alternate interior
angles
Vertical angles
Now if the lines are parallel. . .
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All kinds of special things happen. . .
The corresponding angles postulate (remember
these are true without question) says. . .
 If two parallel lines are cut by a transversal,
then the corresponding angles are congruent.
2
1
3 4
5 6
7 8
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The four pairs of Corresponding
Angles are 
1  5
2  6
3  7
4  8
Tell whether each statement is always (A),
sometimes (S), or never (N) true.
2 and 6 are
supplementary
 1  3
 m1 ≠ m6
 3  8
 7 and 8 are
supplementary
 m5 = m4
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Find each angle measure.
Find each angle measure.
Find each angle measure.
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Determine whether or not l1 ║ l2 , and explain
why. If not enough information is given, write
“cannot be determined.”
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Determine whether or not l1 ║ l2 , and explain
why. If not enough information is given, write
“cannot be determined.”
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Determine whether or not l1 ║ l2 , and explain
why. If not enough information is given, write
“cannot be determined.”
Have you learned .. . .
How to identify the relationships between
two lines or two planes
 How to name angles formed by a pair of
lines and a transversal
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Assignment: Worksheet 3.1