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
Venous angle Venous angle Venous angle (Pirogoff's angle, Latin: "angulus venosus") is the junction of the internal jugular (latin: v. jugularis interna) and subclavian (latin: v. subclavia) veins at both sides of the neck. The external and the anterior jugular and the vertebral veins converge toward it. The left venous angle receives lymph from the thoracic duct (ductus thoracicus). The right venous angle receives lymph from the right lymphatic trunk (truncus lymphaticus). Truncus lymphaticus is only about 1 cm long and conveys lymph from the right side of the thorax (including parts of the liver) as well as the right arm and