Adopt Nick's suggestion for useful default arguments.
Clean-up floating point issues by adding true division and float constants.
diff --git a/Doc/library/random.rst b/Doc/library/random.rst
index 505cc81..a064ac4 100644
--- a/Doc/library/random.rst
+++ b/Doc/library/random.rst
@@ -193,7 +193,12 @@
.. function:: triangular(low, high, mode)
Return a random floating point number *N* such that ``low <= N < high``
- and with the specified *mode* between those bounds.
+ and with the specified *mode* between those bounds.
+
+ If *mode* is not specified or is ``None``, it defaults to the midpoint
+ between the upper and lower bounds, producing a symmetric distribution.
+
+ The default values for *low* and *high* are zero and one.
.. function:: betavariate(alpha, beta)