Inscribed angle its intersection points equals half of the central angle subtended by the chord. See also Tangent lines to circles. The inscribed angle theorem is used in many proofs of elementary Euclidean geometry of the plane. A special case of the theorem is Thales' theorem, which states that the angle subtended by a diameter is always 90°, i.e., a right angle. As a consequence of the theorem, opposite angles of cyclic quadrilaterals sum to 180°; conversely, any quadrilateral for which this is true can be inscribed in a circle. As another example, the inscribed angle theorem is the basis for several
Screen angle depend on how many colors are used and the preference of the press operator, typical CMYK process printing uses any of the following screen angles: Screen angle In offset printing, the screen angle is the angle at which the halftones of a separated color is made output to a lithographic film, hence, printed on final product media. In offset printing, colors are output on separate lithographic plates. Failing to use the correct set of angles to output every color may lead to a sort of optical noise called a moiré pattern which may appear as bands or waves in the