Learn about Polyhedrons In this lesson let’s learn about Polyhedrons and we will learn how to recognize faces, vertices, and edges. The problem gives us two figures and wants us to identify the number of faces, edges and vertices on each of these three dimensional figures, so first lets learn what’s a Polyhedron, a polyhedron is a three dimensional figure, it is a 3-D figure which has flat surfaces. This flat surfaces are called faces, so first lets look at Figure A, how many faces does this cube have, lets I’m going to mark it with different colors this is definitely a face of front, theirs one right behind it. That’s the second one and so every face is got a front and back, the I’ve got one on top, one on the bottom and I’ve got one on this side let’s mark that as red and one on this side. So this apparently has six faces, remember a face is a flat surface so we’ve got one here and one behind it so that’s two, tow of them have marked with the circles and two of them with red strokes, that’s face. Whenever two faces meet, so lets say this face and this face whenever they meet they form an edge, this is an edge so and edge is when two faces meet, how many edges do we have, well I’ve marked one with red, this is two, this is three, this is four, have similarly I’ve got four at the bottom and we’ve got nine, ten, eleven and twelve so looks like we’ve got twelve edges. Remember and edge is when two faces meet, so this face and this face meet at this particular edge and vertices when three faces meet that’s a vertex, the singular for vertices is vertex, whenever three faces meet. So how many points do we have when three faces meet, well we’ve got one here, I’m going to use the blue label here, so we’ve got one here because I’ve got this face, this face and this face meeting right here similarly you got second, third, fourth and at the bottom I’ve got four more. It’s critical to recognize all of them, so you’ve got eight vertices, vertices are plural for vertex. Similarly lets learn how to do the second figure, when we look at the second figure, well this is a pyramid but how many faces will I can count, one two, theirs one behind it three and theirs a bottom one four, so this has four faces. How many edges lets mark those on red, I’ve got six edges and how many vertices, well I can see four vertices. Again the quick thing to recognize is a face is a flat surface, an edge is when two faces meet so this and this face when they meet here that’s an edge and vertex is when three faces meet and we’ve got eight of them here and four of them here. Just quickly one of the things that I did for you is showed you for each of the three dimensional figures, how many flat faces it has, so we look at a prism, square pyramid we look at number of edges, number of vertices etc, when we look at a cube we have six, twelve and eight. So this gives you an idea of how many faces, edges and vertices were suppose to have.