The angles at the circumferenceCircumference is the name of the perimeter of a complete circle, that is, the distance all around it.subtendAn angle created by an object at a given point. by the same arcThe curve between two points on the circumference of a circle. are equal.
More simply, angles in the same segment are equal.
Angles \(a = a\)
Example
Calculate the angles \(p\) and \(q\).
Angles in the same segment are equal.
\(p = 52^\circ\)
\(q = 40^\circ\)
Proof
Let the obtuse angle MOQ = \(2x\).
Using the circle theorem, the angle at the centre is twice the angle at the circumference.