ATAN2(x, y) returns the arctangent of x and y.
This Oracle tutorial explains how to use the Oracle/PLSQL ATAN2 function.
The syntax for the Oracle/PLSQL ATAN2 function is:
ATAN2( n, m )
n and m are the numbers used to calculate the arc tangent.
SQL> select ATAN2(1, -1) from dual;
ATAN2(1,-1)
-----------
2.35619449
SQL>