Polygon Vocab

This video covers your basic everyday polygon vocab stuff: definition of polygon, names of polygons, concave vs convex, equilateral vs equiangular, regular vs irregular (there's also a longer video about regular vs irregular polygons on this page).

Regular vs Irregular

This video covers the basics of regular vs irregular polygons and tells you how to spot them. It also gets into what these terms mean for 3D shapes like prisms and pyramids.

Exterior Angles of Polygons

Even though external angles are a little weirder than interior angles, I like to teach these first because the formulas are so much simpler. First, they always add up to 360 for any polygon, no matter how many sides. And second, they're easy to find for regular polygons, which is the most common type of polygon you come across.

Interior Angles of Polygons

This video covers the "n-2" formula for polygons, but that's not the one you're going to remember a year from now when you're taking admissions tests. The method you're going to remember is breaking up polygons into triangles, which if done properly is the easiest way to go.

Crazy Interior & Exterior Angle Polygon Problems

Other videos introduced interior and exterior angles separately. But this video covers the diciest problems, where you have to figure out which (or both) to use and then figure out the relevant formulas. Sometimes you're even solving for angle X!

Breaking A Concave Polygon Into Triangles

If you forget the n-2 formula for the sum of the internal angles of a polygon, this video covers the next best thing: breaking them into triangles. If done right, this technique is pretty easy, but it's tough to do correctly, especially if the polygon is concave.

How to Find Apothems of Regular Polygons

When you learn to find the area of regular polygons, you are given a formula (A=½ap) that uses something called the "apothem". This video explains how to find the apothem using either SohCahToa or special triangles.

Finding Area of Regular Polygons

This video explains how to find area of polygons using the apothem formula: A=½ap. It also shows you how to find polygon area in a way that you'll actually remember by the time your final rolls around.