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Angles and Properties

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Definition An Angle: – Is made when two lines meet at a common end point. The amount of turning needed to make an Angle is given in Degree’s Angle is 35o

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**Angle Types Acute Angles are between 0o to 90o**

Obtuse Angles are between 90o to180o Reflex Angles are over 180o A Right Angle equals 90o

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**Angle Names The angle shown is called either**

P Q R The angle shown is called either 1) Angle OR 2) Angle OR 3) Angle Note: The middle letter is at the corner or Vertex of the angle.

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**Look at each of these angles.**

Practice Look at each of these angles. Decide if each is A acute, O obtuse or R right-angled. 1 2 A O 3 5 4 A R R 6 7 A A O 8

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**Use the letters to name these angles**

Practice Use the letters to name these angles 1 P T C 2 D R B

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**1 2 3 4 5 6 7 8 9 Acute Acute Obtuse Right Obtuse Reflex Obtuse Acute**

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Measuring Angles

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**What do we use to help us? A protractor**

Here is a standard protractor like you use in the classroom.

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**When we use a protractor, we need to line it up correctly.**

You need to make sure the protractor is lined up correctly. Is this ready to measure the angle?

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**Look for the upside down ‘T’ in the middle of the straight line on your protractor.**

This needs to be exactly on the corner or vertex of your angle.

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**We need to remember..... It doesn’t matter which way round the**

angle is, you ALWAYS need to line the upside down ‘T’ to the vertex of the angle.

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**Read from the 0°, and follow the inner set of numbers.**

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**Once you reach 30° you need to be careful!!!**

You then need to look at the 1° markings on the outer set of numbers.

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What does it measure? This angle measures 35°.

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**Using a Protractor 1 50o 2 67o 0 on the inside so use inside scale**

0 on the outside so use outside scale

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Drawing Angles

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Step One Get a protractor

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Step Two Put 3 dots

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Step Three Move the Protractor

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Step Four Get a ruler

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Step Five Draw a line along the bottom

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Step Six Draw a line along the side

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Step Seven Draw a curved arc between the lines

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**Angles Properties Some angles can be worked out without measuring 1)**

Angles on a straight line add up to 180o a + b = 180o a b E.G a + 50o = 180o a = 130o a 50o

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**Angles around a point add up to 360o**

2) Angles around a point add up to 360o E.G a a a o = 360o a = 150o b 90 c 120 a + b + c = 360o 3) Vertically opposite Angles are equal E.G a b a 80o a = 80o ao = bo

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