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In these lessons, we will look at how to use a protractor to

- draw an angle less than 180˚
- draw an angle greater than 180˚ (reflex angle)

Related Topics:

Construct angles with the use of compasses instead of protractors

More Geometry Lessons

**Example:**

Draw an angle *ABC*, which is 55˚.

** Step 1: ** Draw a line *BC* and mark *B* as the vertex.

** Step 2:** Place the centre of the protractor at the vertex *B *and adjust the base line to be aligned to *BC*.

** Step 3:** Find 55˚ on the outer scale of the protractor and mark that point as point *A*.

** Step 4:** Remove the protractor and draw a line from point *B* to point *A *

** **

**Step 5:** Label and *ABC*

The following video will show you how to draw and measure angles using a protractor.

Measuring Angles

How to measure angles using a protractor.

Measuring angles using a protractor (acute angles).

Measuring Angles with Protractors (obtuse angles).

To draw a reflex angle (i.e. angle greater than 180º and less than 360º), we need to

- Subtract the reflex angle from 360º.
- Draw the resulting angle as described above.
- Mark the required angle which is outside the one that has been drawn.

**Example:**

Draw an angle *ABC *= 250˚

To draw the reflex angle, 250˚, we first draw the angle obtained by subtracting 250˚ from 360˚ which is
360˚ – 250˚ = 110˚

**Step 1****:** Draw the line *BC*

**Step 2****:** Place the centre of the protractor at the vertex *B *and adjust the base line to be aligned to *BC*.

**Step 3****:** Find the angle 110˚ on the protractor (inner) scale and mark that as point *A*.

**Step 4****:** Remove the protractor and draw a line from point *B* to point *A*.

**Step 5****: **Label the reflex angle *ABC*

The following video will show you how to use a protractor to draw acute angles, right angles, obtuse angles and reflex angles.

How to draw a Reflex Angle?

How to Measure a Reflex Angle Using a Protractor?