The ACOS function returns a numeric value in radians that approximates the arccosine of argument-1. The type of this function
is numeric.

- Argument-1 must be class numeric.
- The value of argument-1 must be greater than or equal to -1 and less than or equal to +1.

- The returned value is the approximation of the arccosine of argument-1 and is greater than or equal to zero and less than
or equal to pi.
Note: Conversion factors from radians to degrees and Gon (grad) are specified in the section Trigonometric Functions.
- Floating-point format is used for numeric non-integer results.