RADIUS

(Lat. a ray.) In Geometry and Trigonometry, the semidiaraeter of a circle, or a straight line drawn from the centre to the circumference. In the trigonometrical tables the sines, cosines, tangents, . of circular arcs are expre ed in parts of the radius, which is usually a umed equal to 1. The radius is equal to the side of the inscribed hexagon; or it is equal to an arc of 67-295780, or 57° 17' 44-81", the semi circumferences, or 180°, in parts of the radius 1 being 31415!J27. Radius. In Osteology, a bone of the forearm; so called from its supposed resemblance to the spoke of a wheel. Its upper end, which is the smallest, is formed into a round hollowed head, and is articulated with the small head at the side of the puiley of the humerus, whilst the rounded border of it next the ulna is articulated with the le er sigmoid cavity of that bone; its lower extremity is articulated with the bones of the wrist. [s. 1026]