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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 35 o

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Angle Types Acute Angles are between 0 o to 90 o Obtuse Angles are between 90 o to180 o Reflex Angles are over 180 o A Right Angle equals 90 o

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

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Look at each of these angles. Decide if each is A acute, O obtuse or R right-angled Practice A O R A R O AA

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

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Acute Obtuse Acute Reflex Right Obtuse Acute Reflex Obtuse

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

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Drawing Angles

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Step One

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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 180 o a b a + b = 180 o E.G a 50 o a + 50 o = 180 o a = 130 o

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

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