Introduction to Angles


What will happen if we connect two rays at their endpoints?

1. Select the "ray" from the "line" drop-down menu above. 2. In the workspace, click once to create the endpoint of your ray. 3. Click anywhere else in the workspace to determine the direction of your ray. 4. Select the "ray" option again. 5. Click on the endpoint of your original ray. 6. Click anywhere off of your original ray in the workspace to create the other side of your angle.


Components of Angles

There are several types of angles. To understand the types, we must first understand the components. Below you see ray XY and ray XZ. These two rays are called OPPOSITE RAYS because they are part of the same line and have only their endpoints in common. Opposite rays are form an angle called a STRAIGHT ANGLE because its measure is 180 degrees.

Opposite Rays XY and XZ

Components of Angles Continued

In the angle below... 1. Rays SR and ST are the SIDES of the angle 2. Point S is the VERTEX of the angle

Naming Angles

Angles can be named using either 3 points on the angle or sometimes just the vertex. To name an angle using 3 points, think of it like a ROADMAP. Using a pencil or your finger, trace the angle starting at one point on a side, going to the vertex, then ending at the point on the other side. It is important that you don't pick up your pencil or finger. IMPORTANT: The middle letter is ALWAYS the vertex of the angle!

Practice Naming Angles

In the workspace below, type four different names for the angle.