IORA-00904: Invalid Identifier when converting Radians to Degrees
The DEGREES function you refer to is not in the Oracle database code.  It is in the JavaDB which is also known as Derby.  There is a construct in MySQL called DEGREES so this may be what you were thinking of.

You can make your own function like this

CREATE OR REPLACE FUNCTION radians_to_degree(p_radian IN NUMBER)
   RETURN NUMBER IS
BEGIN
   RETURN p_radian * 0.0174533;
END radians_to_degree;