Acos
Purpose 
Returns the arccosine (Acos), or inverse cosine, of number.
Format 
Acos (number)
Parameters 
number - any numeric expression or field containing a numeric expression in the range -1 to 1
Data type returned 
number
Originated in 
FileMaker Pro 9.0
Description 
The 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.
Examples 
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).
Related topics 
Functions reference (category list)
Functions reference (alphabetical list)
About formulas
About functions
Defining calculation fields
Using operators in formulas