The document discusses properties of arcs, tangents, cyclic quadrilaterals, and chords in circles. It states that the angle at the center of a circle is twice the size of the angle at the circumference on the same arc. For tangents, the angle between the tangent and radius is 90 degrees, and two tangents drawn from an external point are equal. Opposite angles of a cyclic quadrilateral are supplementary, and exterior angles equal interior opposite angles. Properties of chords include equal chords being equal distance from the center and perpendicular bisectors of chords passing through the center.