Returns the arctangent of x and y coordinates as an angle expressed in radians. The first argument is the x coordinate and the second argument is the y coordinate.
Example:
Assume columns HATAN2A and HATAN2B have values of 1 and 2, respectively.
ATAN2(HATAN2A,ATAN2B)
Returns a double precision floating-point number with an approximate value of 1.1071487.