(a) We can name the vertex as B.
(b) We can name the sides as A and C.
The image below shows the angles with their names.
(c) The angle on the left is an obtuse angle because it measures more than 90°. The angle on the right is a right angle because it's equal to 90°.
(e) At last, we name these angles in three ways, using a greek later, using the three letters on the points, or just given the letter of the vertex.
[tex]\begin{gathered} m\angle\alpha \\ m\angle\text{ABC} \\ m\angle B \end{gathered}[/tex]
