A knowledge of arc relationships is required when working with curves in AutoCAD design and programming.Arc relationshipsArc relationships - AutoCAD http://autocad.wikia.com/wiki/Arc_relationships1 di 4 11/05/2012 14.35Arc relationships - AutoCAD http://autocad.wikia.com/wiki/Arc_relationships2 di 4 11/05/2012 14.35Definitionsr=radiusdelta=included angletan(angle)=sin(angle)/cos(angle)Unitsdelta in radians=delta in degrees*pi/180=delta in degrees/57.2957786666 approx.delta in degrees=delta in radians*180/pi=delta in radians*57.2957786666 approx.RelationshipsFor all these relationships, angles are in radians. Angle 2 is the angle of triangle 123 at Point 2Arc length=r*deltaChord=r*tan(delta/2)Bulge=tan(delta/4)=b/(chord/2)=2b/chordTangent=r*tan(delta/2)=r*sin(delta/2)/cos(delta/2)Delta=4*arctan(bulge)R=chord/(2*sin(delta/2)))=arc length/deltaAngle 2 (even when point 2 is not at midpoint of arc)=(2*pi-delta)/2Arc relationships - AutoCAD http://autocad.wikia.com/wiki/Arc_relationships3 di 4 11/05/2012 14.35=pi-(angle1+angle3)=arcsin(chord/(2*R))Arc relationships - AutoCAD http://autocad.wikia.com/wiki/Arc_relationships4 di 4 11/05/2012 14.35