Drawing and measuring angles with a protractor

In a nutshell

Angles are the space between two lines which connect at a point, measured in degrees ($$\degree$$​). They are grouped as acute, obtuse, reflex or right-angles. Angles are measured with a protractor and are always between $$0\degree$$and $$360\degree$$​.

Types of angles

Acute angles are angles less than $$90\degree$$​. 

Right-angles are angles which are exactly $$90\degree$$​. You can see right-angles in many places, such as the corner of a table or a square.

Obtuse angles are angles which are greater than $$90\degree$$​ but less than $$180\degree$$​.

Reflex angles are angles which are greater than $$180\degree$$​. 

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Measuring angles

To measure angles, you can use a tool called a protractor.

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Procedure

Note: If one of the lines is not running along the zero line you won't get an accurate measurement.

Example 1

Measure the angle shown below

Line up the cross-section of the protractor to the corner of the angle. Align the bottom line with the zero line.

As the zero is on the inside, go along the protractor from the inside and stop when you have reached the other line. 

Therefore the angle is $$\underline{45\degree}$$.

Drawing angles

Once you have learned how to measure an angle, drawing them becomes very simple.

Procedure

Note: Always measure the angle you draw afterwards to make sure you did not make any mistakes.

Example 2

Draw a $$40\degree$$angle

Draw a straight base line, and line up the protractor to the point you would like the angle to begin and make a mark on the paper. Go along the zero line to $$40\degree$$ and make a mark on the paper. Remove the protractor, then use a ruler to connect your angle mark to your starting point mark. Check your drawing with a protractor to make sure you've drawn the angle correctly.