Page 13 - Key Stage 3 Geometry

Obtuse angle Reflex angle

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As you can see the acute angle is less than 90 and an
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obtuse angle is greater than 90 and a reflex angle is
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greater than 180 .

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The very special angle is the right angle, this is 90 and
you will come across this angle many times in
geometry and trigonometry. Right angles are

indicated by a small square in the corner. It indicates
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that one line is perpendicular to the other (90
between them).

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Angles occur in the range 0 to 360 if you are moving
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in a clockwise direction or 0 to -360 if moving in an
anticlockwise direction. Very often you will see the
Greek letter theta θ used to label an angle. Therefore,

0 ≤ ≤ 360
The symbol ≤ means small than or equal to. This

expression is a way of say that the angle θ lies in the
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range of 0 to 360 .
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