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Maths

Geometry - properties of shapes

Right angles, acute and obtuse angles

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Angles are measured in degrees ($\degree$). A right angle measures 90$\degree$, and can be used to describe turns.

A right angle measures 90$\degree$. You can measure angles with a protractor. A right angle can also be described as a quarter of a turn.

If you turn around once fully, you will have turned 360$\degree$. Therefore:

Note: A half-turn (180$\degree$) is also called an "angle on a straight line".

Apart from right angles, there are other angles to consider:

Acute angles are less than 90$\degree$:

Obtuse angles are greater than 90$\degree$ but less than 180$\degree$:

Reflex angles are more than 180$\degree$ but less than 360$\degree$:

Here are all the angles together:

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4 Exercises

Reflex angles are more than 180 degrees but less than 360 degrees.

4 right angles make a full turn.

2 right angles make a half-turn.

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