basics of geometry 1.4 intersections 1.5 segments
TRANSCRIPT
Basics of Geometry1.4 Intersections
1.5 Segments
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
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
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
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
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
Sketch It!
Sketch and label two planes that intersect.
S
Rk
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
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
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
Find AB
-5 13A B
12 xxAB )5(13 AB 18
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
Find EF
D E F
16
10
EFDEDF EF1016
10101016 EFEF6
Find AB
C A B
29
15ABCACB AB1529
15151529 ABAB14
Find DF
D E F12
EFDEDF 712 DF
19DF
7
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
Congruent Segments
Congruent segments are often marked with a short tick mark.
A B
C D
CDAB
Congruent Segments
Sometimes multiple tick marks will be used.
R S
TH
HTRS STRH
Assignment
Pages 31 – 33
1 – 28