Reference > Functions reference > Trigonometric functions > Acos


Returns the arccosine (Acos), or inverse cosine, of a number.


Acos (number)


number - any numeric expression or field containing a numeric expression in the range -1 to 1

Data type returned 


Originated in 

FileMaker Pro 9.0


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.

Example 1 

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)

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About functions

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