Document the optional second arg of `atan'.

1 files changed, 7 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 6ab8d2b2bcb..00f15dfd5b6 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -626,6 +626,13 @@ 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.
 
 A window that is just one line tall does not display either a mode