AcosFileMaker Pro 9.0The arccosine is the angle whose cosine is number. The returned angle is given in radians in the range 0 (zero) to Pi. The input number parameter must be between -1 and 1.If you want to convert the result from radians to degrees, multiply it by 180/Pi or use the Degrees function.Acos(-0.5) returns 2.0943951.Acos(-0.5)*180/Pi returns 120.Degrees(Acos(-0.5)) returns 120.Acos(2.0)returns ? (not a number).