Download 1‐3: Measuring Segments Ruler Postulate

1‐3:Measuring
Segments
RulerPostulate
• Every point on a line can be paired with a real one-to-one
number. This makes a ____________ correspondence
___________________ between the points on the line and the real numbers. The real number that coordinate
corresponds to a point is called the ____________ of the point.
What’s the distance between A and B?
a 1
b3
3 1  2
A
B
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DistanceFormula(onanumberline)
• Take the absolute value of the difference of the coordinates of two points:
AB  a  b
AB means the distance
from A to B
Example 1: What is CD?
B
C
D
2
10
CD  c  d
E
CD  2  10
CD  10  2
CD  8  8
CD  8  8
• Postulate 1‐6: Segment Addition Postulate
• If three points A, B and C are collinear and B is between A and C, then: AB  BC  AC
AC
A
B
C
BC
AB
Example 2: If LN=32, what are LM and MN?
L
3x  8
M
2x  4
N
Complete Got It? #2 p.21
3 x  8  2 x  4  32
LM  3(4)  8  20
JK  42
5 x  12  32
MN  2(4)  4  12
KL  78
5 x  20
x4
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Vocabulary
• Congruent Segments
• Two or more segments that have the same length
• Symbol ≅
• Midpoint
• Point that divides a segment into two congruent segments.
• Segment Bisector
• Point, line, ray or other segment that intersects a segment at its midpoint.
• Divides segment into two equal length segments.
AC
RT
Example3:isasegmentbisectorof.
RS
,
ST
and
RT
?
Whatare
C
What do you know?
RS  ST
How do you use what you know?
7 x  3  3x  1
Solve
7 x  3  3x  1
4x  4
x 1
R
7x  3
S
3x  1
T
A
Substitute
RS  7(1)  3  4
ST  3(1)  1  4
RT  4  4  8
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Homework:p.24#’s10‐16,19‐22,25‐29,39,43,48‐56even
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