basics of geometry 1.4 intersections 1.5 segments
TRANSCRIPT
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Basics of Geometry1.4 Intersections
1.5 Segments
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ReviewThe intersection of two lines is a
___________.The intersection of two planes is
a ________.Any three points can define a
___________.Any two points can define a
________.
LINE
LINE
POINT
PLANE
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Review Name 4 coplanar
points. Are A, D, and E
coplanar? Are A, D, G, and F
coplanar? Are E and F collinear? Give plane ADC
another name.
A
B C
D
E F
GH
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Intersections of Lines Name the intersection
of and Name the intersection
of and Name the intersection
of and
AC BE
AC
BE DF
DF
A B C
D E F
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Intersections of Planes Name the intersection
of planes S and R. Name the intersection
of planes R and T. Name the intersection
of planes T and S.
S
R
T
k
l
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Sketch It!
Sketch and label a plane. Draw and label a line that is in the plane. Draw and label a line that does not
intersect the plane. Draw and label a line that intersects the
plane at one point.
Pj
lk
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Sketch It!
Sketch and label two planes that intersect.
S
Rk
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Assignment :
First, we will discuss page 17.
Then, quietly work on your own work. I will help if you need it.
p. 11: 8, 14, 24, 36, 38
p. 17: 16 – 32 even
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Segments
A segment is a part of a line. A segment has a length. To find the length of a segment (or the
distance from beginning to end), subtract the coordinates of the endpoints and take the absolute value.
12 xx
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Segments Continued
The notation for distance is simply the endpoints of the segment.
Thus, the formula for distance on a line segment is:
AB
12 xxAB
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Find AB
-5 13A B
12 xxAB )5(13 AB 18
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Segment Addition Postulate
If B is between A and C, then AC = AB + BC
If AC = AB + BC, then B is between A and C
A B C
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Find EF
D E F
16
10
EFDEDF EF1016
10101016 EFEF6
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Find AB
C A B
29
15ABCACB AB1529
15151529 ABAB14
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Find DF
D E F12
EFDEDF 712 DF
19DF
7
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Congruency
Shapes that have the same dimensions are called congruent.
Two segments who have the same length are called congruent.
The symbol for congruency is
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Congruent Segments
Congruent segments are often marked with a short tick mark.
A B
C D
CDAB
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Congruent Segments
Sometimes multiple tick marks will be used.
R S
TH
HTRS STRH
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Assignment
Pages 31 – 33
1 – 28