An angle is a measurement of turn It tells us the amount of turn … · 2016-09-29 · The angles...
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An angle is a measurement of turn. It tells us the amount of turn from one position to another. www.teachingpacks.co.uk Images: © ThinkStock ©
Transcript of An angle is a measurement of turn It tells us the amount of turn … · 2016-09-29 · The angles...
An angle is a measurement of turn.It tells us the amount of turn
from one position to another.
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©
Some angles have special names that you need to remember.
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Whole Turn(360º)
Straight Line(or straight angle)
(180º)
Right Angle(90º)
Acute Angle(less than 90º)
Obtuse Angle(between 90º and 180º)
Reflex Angle(more than 180º)
You can use these to estimate the size of unknown angles.
We can use a protractor to measure the size of an angle.It can be helpful to make a sensible estimate first.
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41
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This angle is acute. My estimate is 70º.
Place the cross of the protractor on top of the corner of the angle.
Line up the bottom line of the protractor with one of the lines of the angle.
Starting at 0º, count up to the angle’s other line and read the measurement.This angle is 67º.
Did you notice that the protractor has two scales?Remember to start counting at the correct 0º.
When you are reading the
measurement, check that your
protractor hasn’t moved!
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The angles inside a triangle always add up to 180º.
70o 70o
40o
60o90o
30o
30o
107o
43o
40o + 70o + 70o = 180o 30o + 90o + 60o = 180o 30o + 107o + 43o = 180o
If you know two of the angles inside a triangle,you can use this fact to calculate the third angle...
... and if the triangle is an isosceles triangle, you can calculate the other angles if you only know one of them!
1. 2.
3. 4.
5. 6.
7. 8.
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A
1.
Right
2.
Acute3.
Obtuse
4.
Acute5.
Obtuse
6.
Acute7.
Obtuse
8.
Obtuse
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AAnswers
1degrees Acute
5degrees Acute
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12degrees Acute
15degrees Acute
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25degrees Acute
32degrees Acute
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©
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