Inscribed angle "V" and whose sides pass through points "A" and "B". Draw line "OA". Angle "BOA" is a central angle; call it "θ". Lines "OV" and "OA" are both radii of the circle, so they have equal lengths. Therefore, triangle "VOA" is isosceles, so angle "BVA" (the inscribed angle) and angle "VAO" are equal; let each of them be denoted as "ψ". Angles "BOA" and "AOV" are supplementary. They add up to 180°, since line "VB" passing through "O" is a straight line. Therefore, angle "AOV" measures 180° − "θ". It is known that the three angles of a triangle add
Antiparallel (mathematics) and only if they make the same angle formula_18 in the opposite senses with the bisector of that angle (Fig.3). In a Euclidean space, two directed line segments, often called "vectors" in applied mathematics, are antiparallel, if they are supported by parallel lines and have opposite directions. In that case, one of the associated Euclidean vectors is the product of the other by a negative number. Antiparallel (mathematics) In geometry, anti-parallel lines can be defined with respect to either lines or angles. Given two lines formula_1 and formula_2, lines formula_3 and formula_4 are anti-parallel with respect to formula_1 and formula_2