An angle whose vertex is at the center of a circle is a middle angle of that circle.
a. true
b. false

An angle whose vertex is at the center of a circle is a middle angle of that circle.  

This is false because there can be numerous angles in the center of a circle. Moreover, the angle whose vertex is at the center is called a central angle. The two endpoints of this angle and located at the circumference or outline of the circle and the vertex is located at the center of that circle.

you need to give us more information since we can't answer