theorem 1
angles in the same segment are equal
theorem 2
the angle at the centre is twice the angle at circumference
theorem 3
opposite angles in a cyclic quadrilateral add to 180 degrees
theorem 4
alternate segment theorem
theorem 5
the angle in a semi circle is a right angle
theorem 6
the tangents to a circle is perpendicular to the radius
theorem 7
two tangents to a circle from a point are equal
theorem 8
the perpendicular from the centre to the chord bisects the chord