Post on 30-May-2018
8/14/2019 Degrees: Measuring Angles
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Degrees: Measuring Angles
We measure the size of an angle using degrees.Example: Here are some examples of angles and
their degree measurements.
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Protractor A device used to measure angles.
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Reading a ProtractorDate: 9/8/96 at 22:29:58 From: Bob Vanselow
Subject: Reading a Protractor Which side of a protractorscale do you use?
Date: 9/9/96 at 11:39:23 From: Doctor RobertSubject: Re: Reading a ProtractorI think that the easiest way to decide which scale to use is to look at the
angleyou're measuring. If it is greater than a right angle (more than ninetydegrees)then use the scale that has numbers greater than 90. If the angle is obvacute (measures less than 90 degrees), use the scale which has numbeless than 90. Of course you have to line up the protractor correctly with
the center point on the vertex of the angle and one of the rays of the ancoincide with the line on the protractor. Happy measuring!-Doctor Robert, The Math Forum Check out our web site!http://mathforum .org/dr.math/
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Acute Angles
An acute angle is an angle measuring between 0and 90 degrees.
Example:
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Obtuse Angles
An obtuse angle is an angle measuring between 90 and180 degrees.
Example:
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Right AnglesA right angle is an angle measuring 90 degrees.
Examples:
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Complementary AnglesTwo angles are called complementary angles if thesum of their degree measurements equals 90 degrees.
Example:
These two angles are complementary.
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These two angles can be "pasted"
together to form a right angle!
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Supplementary AnglesTwo angles are called supplementary angles if the sumof their degree measurements equals 180 degrees.
Example: These two angles are supplementary.
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These two angles can be "pasted"together to form a straight line!
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Vertical Angles
For any two lines that meet, such as in the diagram below,angle AEB and angle DEC are called vertical angles.Angle BEC and angle AED are also vertical angles.Vertical angles have the same degree measurement .
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Review
State whether the following are acute, right, or obtuse.1.
2.
3.
4.
5.
??
acute obtuseright
obtuseacute
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Complementary andSupplementary
1. Two angles are complementary. One measures 65 degrees.
2. Two angles are supplementary. One measures 140 degrees.
Find the missing angle.
Answer : 25
Answer : 40
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Complementary and
Supplementary
Find the missing angle. You do not have a protractor.
Use the clues in the pictures.1. 2.x
55 165x
X=35 X=15
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Vertical Angles
Find the missing angle. You do not have a protractor.
Use the clues in the pictures.
58 xX=58
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More drawings
20
C
J
D
E F
G
H
70
907020
90
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Final Drawing
52
B
A
F E
D
C
60
G
68
68 6052