The ATAN2 function returns the arc tangent of x and y coordinates
as an angle expressed in radians. The first and second arguments specify
the x and y coordinates, respectively.

>>-ATAN2--(--expression-1--,--expression-2--)------------------><
- expression-1
- An expression that returns a value of any built-in numeric data
type (except for DECFLOAT), character-string, or graphic-string data
type. A string argument is cast to double-precision floating point
before evaluating the function. For more information on converting
strings to double-precision floating point, see DOUBLE_PRECISION or DOUBLE. If one argument is 0, the other
argument must not be 0.
- expression-2
- An expression that returns a value of any built-in numeric data
type (except for DECFLOAT), character-string, or graphic-string data
type. A string argument is cast to double-precision floating point
before evaluating the function. For more information on converting
strings to double-precision floating point, see DOUBLE_PRECISION or DOUBLE. If one argument is 0, the other
argument must not be 0.
The data type of the result is double-precision floating
point. If any argument can be null, the result can be null; if any
argument is null, the result is the null value.