Central angle intersection points and of the legs of the angle with the circle form a diameter, then is a straight angle. (In radians, .) Let be the minor arc of the circle between points and , and let be the radius of the circle. If the central angle is subtended by , then If the central angle is not subtended by the minor arc , then is a reflex angle and If a tangent at and a tangent at intersect at the exterior point , then denoting the center as , the angles (convex) and are supplementary (sum to 180°). A
Etiquette in Japan from the waist with the back and neck straight, hands at the sides (males) or clasped at the lap (females), and eyes looking down. The body should be composed but not rigid. Generally, the longer and deeper the bow, the stronger the emotion and respect expressed. The three main types of bows are informal, formal, and very formal. Informal bows are made at about a fifteen-degree angle or just tilt over one's head to the front, and more formal bows at about thirty degrees. Very formal bows are deeper. The etiquette surrounding bowing, including the length, depth, and appropriate response,