what do we use to measure the angle? protractor angles, measuring angles the unit of measurement of...
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What do we use to measure the angle?
PROTRACTOR
Angles, Measuring Angles
The unit of measurement of an angle is degrees.
We measure angles in degrees.
90 degrees is written as 900.
Zero line or base line Center or origin
Angles, Measuring Angles
Parts of Protractor
Scale
Angles, Measuring Angles
The scale at the outside is called outer scale.
Scale of Protractor The scale at the inside is called inner scale.
00 of outer scale
00 of inner scale
You can measure an angle using the outer or inner scale depending where you put the arm.
What is the arm?
Angles, Measuring Angles
Line A
Scale of Protractor
arm
The line that you will place on the base line
or zero line of the protractor is called
the arm.
Angles, Measuring Angles
Line A
Scale of Protractor
arm
The line that you will place on the base line
or zero line of the protractor is called
the arm.
Angles, Measuring Angles
Line A
Why not 1200?Because the 00 of the inner scale lies on Line A or the arm.
Scale of Protractor
600
Start counting at 0O from the
arm.
It can be 0o of the inner
scale or outer scale.
arm
How wide is the
angle?
600
Angles, Measuring Angles
Line B
Why not 1200?Because the 00 of the outer scale lies on Line B or the arm.
Scale of Protractor
Start counting at 0O from the
arm.
It can be 0o of the inner
scale or outer scale.
arm
How wide is the
angle?
Measuring an angle
A
BC
vertex
1st step: place the zero line or base line of the protractor on one side of the angle or the arm.
2nd step: place the center at the vertex of the angle.
70o
Angles, Measuring Angles
3rd step: read off the outer scale.
Example 1
arm
Measuring an angle
A
BC
vertex
70o
Angles, Measuring Angles
Example 1
Why 700?
Start reading
armarm
Measuring an angle
A
BC
vertex
Angles, Measuring Angles
Example 1
Start reading Why
700?
arm
Measuring an angle
A
BC
vertex70o
Angles, Measuring Angles
Example 1
End reading Why
700?
arm
A
BC
vertex
60o
Measuring an angle
1st step: place the zero line or base line of the protractor on one side of the angle or the arm.
2nd step: place the center at the vertex of the angle.
Angles, Measuring Angles
3rd step: read off the inner scale.
Example 2
arm
A
BC
vertex
Measuring an angleAngles, Measuring Angles
Example 2
Why 600?
Start reading
armarm
A
BC
vertex
Measuring an angleAngles, Measuring Angles
Example 2
Why 600?
Start reading
arm
A
BC
vertex
Measuring an angleAngles, Measuring Angles
Example 2
Why 600?
End reading
arm
60o
Measuring an angle
A
BC
vertex
1st step: place the zero line or base line of the protractor on one side of the angle or the arm.
2nd step: place the center at the vertex of the angle.
70o
Angles, Measuring Angles
3rd step: read off the inner scale.
Example 1, alternative
arm
A
BC
vertex
60o
Measuring an angle
1st step: place the zero line or base line of the protractor on one side of the angle or the arm.
2nd step: place the center at the vertex of the angle.
Angles, Measuring Angles
3rd step: read off the outer scale.
Example 2, alternative
arm
R =
R
80o S = 67o
S
W
W = 31o
Measuring an angleAngles, Measuring Angles
Example 3