Oracle PL/SQL/Numeric Math Functions/ATAN2

ATAN2(x, y):Returns the arctangent of x and y

SQL>
SQL> --ATAN2(x, y):Returns the arctangent of x and y.
SQL>
SQL> select ATAN2(1, -1) from dual;
ATAN2(1,-1)
-----------
 2.35619449
SQL>

ATAN() and ATAN2() functions are return some the arctangent

 
SQL>
Syntax:
ATAN(<numeric expression>)
ATAN2(<numeric expression1>,<numeric expression2>)
SQL>
SQL>
SQL>
SQL> SELECT    ATAN(.5) AS FIRST_RESULT,
  2     ATAN2(.5,1.0) AS SECOND_RESULT
  3  FROM DUAL;
FIRST_RESULT SECOND_RESULT
------------ -------------
  .463647609    .463647609