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Measuring angles in degrees

Measuring angles in degrees

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Summary

Measuring angles in degrees

In a nutshell

An angle is formed when two lines meet at a shared point. Angles are measured in degrees (°\degree), which can be measured with a protractor.


Angles and measurement

The degree (°\degree) is the unit of measurement for angles. There are 90°90\degree in a right angle, and 360°360\degree in a full circle. A protractor is a tool used to measure how many degrees are in an angle.


Acute angles

Here are the steps for how to measure an acute angle with a protractor:


Procedure

1.

Place the midpoint of the protractor on the vertex of the angle.

2.

Line up one side of the angle with the zero line of the protractor (where the number 00​ appears).

3.

Read the degrees where the other side of the angle crosses the number scale.


Example 1


In the example above, the acute angle has a measurement of 40°\underline{40\degree}.


Obtuse angles

Here are the steps for how to measure an obtuse angle with a protractor:


Procedure

1.

Place the midpoint of the protractor on the vertex of the angle.

2.

Line up one side of the angle with the zero line of the protractor (where the number 00​ appears).

3.

Read the degrees of the other side of the angle, and subtract this value from 90°90\degree.​

4.

Add the 90°90\degree to the previous value to find the overall obtuse angle.​


Example 2
Maths; Geometry - properties of shapes; KS2 Year 5; Measuring angles in degrees


In the example above, the obtuse angle has a measurement of 110°\underline{110\degree} because:

(90°70°)+90°=110°(90\degree - 70\degree) + 90\degree = \underline{110 \degree}


Reflex angles

Here are the steps for how to measure a reflex angle with a protractor:


Procedure

​​1.

Place the midpoint of the protractor on the vertex of the angle.

2.

Measure the smaller angle on the other side of the reflex angle, with the same method as described above for an obtuse angle.

3.

Subtract this smaller angle from 360°360\degree to give the value of the reflex angle.​


Example 3
Maths; Geometry - properties of shapes; KS2 Year 5; Measuring angles in degrees


In the example above, the reflex angle has a measurement of 320°\underline{320\degree} because:

360°40°=320°360\degree-40\degree=\underline{320\degree}



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FAQs - Frequently Asked Questions

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