Answer: You can know which is the Central angle by identifying that angle whose vertex is located at the center of the circle and formed when two radii meet (These radii also intersect the circumference of the circle in two points).
See the picture attached
Step-by-step explanation:
Since you did not attached the figure, I will give you a general explanation about how to identify that Central angle in a circle:
First, it is important to know the definition of "Central angle".
The Central angle of a circle is that angle formed when two radii meet. These radii intersect at the center of the circle and also intersect circumference of the circle in two points.
The above means that the vertex of the Central angle is located at the center of the circle.
In the picture attached you can identify that the Central angle of the circle is the following:
By definition, it is known that:
In this case:
