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Published byBarry Miles Modified over 8 years ago
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An angle is a corner where two lines meet. Angles are drawn with a small part of a circle in the corner. Angles can be measured in degrees with a protractor. There are 5 names given to angles depending on how big they are.
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Acute angles are the sharpest angles. They are between _____ and _____. 090
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Right angles are like the corners of a square. They are exactly _____ degrees. They are marked with a square instead of a circle. 90
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Obtuse angles are between ______ degrees and ______ degrees. 90 180
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Straight angles are exactly ______ degrees 180
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Reflex angles are between ______ and ______ degrees. 180 360
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Angles are named using three letters. The middle letter shows where the angle is. The other two letters show the sides that make up the angle. The angle in the picture Is angle ABC.
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Sometimes a symbol like a capital L is in front of the three letters. This symbol means “angle”. A small symbol can be drawn over the middle letter instead.
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We can use rules about shapes to calculate unknown angles.
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Angles on a straight line add up to 180 degrees. 120 60 105 75
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Angles around a point add up to 360 degrees. 70 290 160 70 130
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Angles inside a triangle add up to 180 degrees. 40 75 65 100 50 30
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Angles inside a quadrilateral (4 sides) add up to 360 degrees. 40 50 110 160 80 130 60 90
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Vertically opposite angles are equal. When two straight lines cross over the opposite angles are equal. 120 60
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Rules 6, 7 and 8 are about the angles made when a line cuts through two parallel lines. This line makes 8 angles.
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Rules 6, 7 and 8 are three rules called; Alternating Angles, Corresponding Angles, and Co-Interior Angles Basically they all work on the same 2 ideas. 1.When you have angles on parallel lines that look the same, they are the same. 2.If the angles look different, they add up to180 degrees.
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Alternating angles are equal. Alternating means they swap the side of the line. Left to right or right to left.
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Corresponding angles are equal. Corresponding means they are exact copies just on the next line.
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Co-interior angles add up to 180. Co-interior means both angles are inside the parallel lines next to each other
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The outside (exterior) angles of any shape always add up to 360 degrees. So in regular shapes each angle is 360 ÷ sides.
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95 o 120 o 145 o
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