Document the optional second arg of `atan'.

diff --git a/etc/NEWS b/etc/NEWS
index 6ab8d2b2bcb175a2c1bad1d4233a1a898677db8e..00f15dfd5b6e1dbedced49f282a3b99465f4a294 100644 (file)
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -625,6 +625,13 @@ and the latter now controls scrolling down.
 This is like window-height but does not count the mode line
 or the header line.
 
++++
+** The function `atan' now accepts an optional second argument.
+
+When called with 2 arguments, as in `(atan Y X)', `atan' returns the
+angle in radians between the vector [X, Y] and the X axis.  (This is
+equivalent to the standard C library function `atan2'.)
+
 +++
 ** You can now make a window as short as one line.