 In this video we're going to look at the angles in polygons. We're going to look at the sum of interior angles and the size of one interior angle. We'll look at exterior angles in another video. Before we start you should already know the names of different types of polygons. If you're unsure you may want to watch this video first. You probably already know that if we add up all three angles in a triangle we get 180 degrees. Working from one corner quadrilaterals can be split into two triangles so 180 times 2 means there are 360 degrees in any quadrilateral. All pentagons split into three triangles so three times 180 means they have 540 degrees. What do you think my angles in an octagon add up to? Pause the video and whack it out. Octagons split into six triangles and so six times 180 means there are 1,080 degrees in all octagons. For any polygon there are always two less triangles then there are numbers of sides so five sides times three six sides times four. We've just seen that we can easily work out the sum of interior angles for any type of polygon it can be regular or irregular but to work out the size of one interior angle it has to be a regular polygon. Regular polygons have all equal sides and angles whereas irregular are different. The sum of interior angles for a pentagon is 540 so 540 divided by five angles is 108 degrees each. What is the size of one angle in a regular heptagon? Pause the video and whack it out. Did you get 128.6 degrees? So here are some questions for you to do. Pause the video, whack them out and click play when you're ready. So there we have the interior angles of polygons. You simply need to know that there are 180 degrees in a triangle. We then look to see how many triangles fit into the polygons. There's always two less triangles than there are numbers of sides. If you liked the video give it a thumbs up and don't forget to subscribe. Comment below if you have any questions. Why not check out our Fusco app as well. Until next time.