April 13, 2023

Angles

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1. Angle facts

April 13, 2023

The sum of the angles on a straight line is always 180º.

140º

40º

You can describe this rule using letters.

40 + 140 = 180

ba

a b

Explanation

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April 13, 2023

40º

The sum of the angles round a point is always 360º.

140º

140º

40º

You can describe this rule using letters.

a + b + c + d 140 + 40 +140 + 40 = 360

a

bc

d

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Explanation

April 13, 2023

40º

When two lines cross, the opposite angles are equal.

140º

140º

40º

You can describe this rule using letters.

a

b

a = b c = d

c d

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Explanation

April 13, 2023

The sum of the angles inside a triangle is always 180º.

You can describe this rule using letters.

a + b + c = 180

a

b

c

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Explanation

April 13, 2023

Right-angle

ScaleneEquilateral

Isosceles

These are the four types of triangle.

Equal sides can be shown using a small ‘dash’.

Revise

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April 13, 2023

ba

The sum of the angles in a quadrilateral is always 360º.

63º

104º124º

69º

= 360NextNextMoreMore

+ + +c d

a

b

cd

69 63 104 124

Explanation

April 13, 2023

The angles in this quadrilateral still add up to 360º, even though it is a re-entrant shape.

You can see this if you think of it as two triangles.

180 + 180 = 360

Explanation

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April 13, 2023

Find the missing angles.

ab

c144º

88º132º

78º

65º

144º46º

85º

Practise

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