Naming Angles

Angles can be named in several ways. The simplest is to label the vertex with a single letter preceded by a slanting L:


When angles share sides we can place numbers inside (close to the vertex). For example, angles 1 and 2 share the common vertex A:


We also use little arcs centered at the vertex with tick-marks to indicate angles that have the same measure. Here angles 1 and 2 are equal (in measure):


You can also name an angle using three letters, where the middle letter is the vertex and the other two are points on the sides: