# Internal angles in a quadrilateral

In this lesson, you will be able to use triangles to deduce the sum of the interior angles in a quadrilateral. You will also be able to find unknown angles in quadrilaterals.

# Video

Click on the play button to start the video. If your teacher asks you to pause the video and look at the worksheet you should:

- Click "Close Video"
- Click "Next" to view the activity

Your video will re-appear on the next page, and will stay paused in the right place.

# Worksheet

These slides will take you through some tasks for the lesson. If you need to re-play the video, click the ‘Resume Video’ icon. If you are asked to add answers to the slides, first download or print out the worksheet. Once you have finished all the tasks, click ‘Next’ below.

# Lesson summary: Internal angles in a quadrilateral

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The next lesson in Classifying 2-D shapes is "Tessellating quadrilaterals"