Vertex of an angle

Definition

A point where two straight lines meet each other to form an angle is called the vertex of an angle.

Introduction

A straight line starts from a point on a plane. Two or more lines can be started from that point and then, they continue travelling straightly in different directions. The point is their meeting point and an angle is formed between every two straight lines by their meeting. So, the point is called the vertex of an angle.

Look at the above graphic animation to understand what the vertex of an angle really is. Now, let’s learn more about the vertex of an angle practically.

Example

Let’s learn the concept of the vertex of an angle in geometric system.

1. Let’s consider a point on a plane and denote it by $O$.
2. Draw a straight line from point $O$ and assume that it passes through a point $P$.
3. Similarly, draw another straight line from point $O$ and assume that it passes through a point $Q$.

The point $O$ is origin for both rays $\overrightarrow{OP}$ and $\overrightarrow{OQ}$. It seems that it is their meeting point, and an angle is formed between them at that point.

Therefore, the point $O$ is called the vertex of an angle formed by the straight lines $\overrightarrow{OP}$ and $\overrightarrow{OQ}$.