postgres=#
postgres=# -- atan2(x, y): Returns the inverse tangent of the quotient of x and y
postgres=# SELECT atan2(0, 1), atan2(1, 1),
postgres-# atan(0 / 1) AS functionally,
postgres-# atan(1 / 1) AS identical;
atan2 | atan2 | functionally | identical
-------+-------------------+--------------+-------------------
0 | 0.785398163397448 | 0 | 0.785398163397448
(1 row)
postgres=#