A straight line that divides the circle into two semi-circles.It is called the diameter of the circle.
An arc whose measure equals is called a semicircle, since it divides the circle in two. Every pair of endpoints on a circle either defines one minor arc and one major arc, or two semicircles. Only when the endpoints are endpoints of a diameter,then the circle is divided into semicircles.
Hence, in a circle is a semicircle which makesangle on center.
