Question

Degree measurement theorem proof

Answer 1

The angle subtended at the centre of a circle is double the size of the angle subtended at the edge from the same two points,Angles which are in the same segment are equal, i.e. angles subtended (made) by the same arc at the circumference are equal,The angles which are within a semicircle add up to 90°,Opposite angles in a cyclic quadrilateral add up to 180°,Alternate Segment Theorem, i.e. that the angle between a tangent and its chord is equal to the angle in the 'alternate segment