Function ACOS(2) and ASIN(2) should be null

hive> desc function extended acos;
OK
acos(x) - returns the arc cosine of x if -1<=x<=1 or NULL otherwise
Example:
  > SELECT acos(1) FROM src LIMIT 1;
  0
  > SELECT acos(2) FROM src LIMIT 1;
  NULL
Time taken: 0.009 seconds, Fetched: 6 row(s)
hive> select acos(2);
OK
NaN
Time taken: 0.437 seconds, Fetched: 1 row(s)

mysql>  select acos(2);
+---------+
| acos(2) |
+---------+
|    NULL |
+---------+
1 row in set (0.00 sec)