“How can we classify the point where two lines meet?”
When working with Geometry, We will have to deal with alot of different and divergent phenomena. In order to organize all of this for practical use, we will have to give such special phenomena special terminology. So let’s do an example with the intersection of two lines.. Geometers (Mathematicians who research geometry) have decided to name this intersection a vertex. Since all vertices involve the intersection of two lines, vertices always include an angle.
But let’s not limit ourselves to just simple lines, let’s look at an interesting application of vertexes to more complex three dimensional structures. When two vertices meet in a polyhedron, a mathematical object called an edge is formed. But what is even more fascinating is that if you take all of the faces (the 2-dimensional shapes that make up the outer surface) of a polyhedron, and add the difference of the Vertices and angles, the answer will always equal two! We can represent this symbolically as F+E-V = 2