1.2 Measurement of Segments and Angles. Measuring Segments Match item being measured with proper...
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Transcript of 1.2 Measurement of Segments and Angles. Measuring Segments Match item being measured with proper...
1.2 Measurement of Segments and Angles
Measuring Segments
Match item being measured with proper unit.
U.S.: Inches, feet, yards, miles etc.Metric: km, cm, m, mm
Distance: absolute value
m AB1 2 3 4
A B
|2-3| or |3-2|= |-1| = |1|= 1 = 1
The length of AB = 1 cm
cm
Measuring angles:
Unit of measure:DegreesRadiansGrads
Tool: protractor
Angle measurement
Angle measurement is the opening from one ray to the next ray.We usually use the inside measurement, 180° or less.
A full turn is a circle and measures 360°.
PA R
m<PAR = 90m<A = 90
Angle measurement
m<1 = 1351
Classify angles by size
Acute: 0<x<90
Right: 90 Obtuse: 90<x<180
Straight: 180
Parts of a degree:
1 Degree = 60’ (minutes)1 Minute = 60” (seconds)So, 87 = 8730’
12
90 = 8959’60”
Find m<CBD
A
B
C
D
m<ABD = 90
m<ABC = 7421’10”
90
- 7421’ 10” 1538’50”
8959’ 60”- 7421’ 10”
Congruent angles and segments
Symbol: == < have the same measure= have the same length
<A = <B
A 60 B 60
Congruency
Tick marks show congruencyA
CB
X
Z Y
Name congruent angles and segments.
ExampleAB
C
12
m<ABC = 90
m<1 = (3x+4)m<2 = (x+6)
Find both angles!
3x + 4 + x + 6 = 904x + 10 = 904x = 80x = 20
m<1 = 64°m<2 = 26°
Find the measure of the angle formed by the hands of a clock at
5:15.• The hour hand is on 5 only when the minute hand is on 12.
• How far will the hour hand be away from 5 when it is 5:15?
• It will be ¼ of the way between the 5 and the 6.
• How many degrees is that?• There are 360º in the clock. Every 5
minutes has how many degrees?• ¼ of 30 is • How many “5 minute” intervals do
you need to add to that?• The angle measure of 5:15 is 67.5º.
7.5º
2 intervals for a total of 60º.
30º