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
Pressure angle force along the pitch line which is responsible for power transmission is proportional to the cosine of pressure angle. The one which exerts thrust (perpendicular to the pitch line) is proportional to the sine of pressure angle. So it is advised to keep the pressure angle low. Standard pressure angles are 14.5 and 20 degrees. Just as there are three types of profile angle, there are three types of corresponding pressure angle: the transverse pressure angle, the normal pressure angle, and the axial pressure angle. Pressure angle Pressure angle in relation to gear teeth, also known as the angle of