#6765: hint that log(x, base) is not very sophisticated.
diff --git a/Doc/library/math.rst b/Doc/library/math.rst
index 4d566a5..96ea91a 100644
--- a/Doc/library/math.rst
+++ b/Doc/library/math.rst
@@ -166,8 +166,10 @@
.. function:: log(x[, base])
- Return the logarithm of *x* to the given *base*. If the *base* is not specified,
- return the natural logarithm of *x* (that is, the logarithm to base *e*).
+ With one argument, return the natural logarithm of *x* (to base *e*).
+
+ With two arguments, return the logarithm of *x* to the given *base*,
+ calculated as ``log(x)/log(base)``.
.. versionchanged:: 2.3
*base* argument added.
@@ -183,7 +185,8 @@
.. function:: log10(x)
- Return the base-10 logarithm of *x*.
+ Return the base-10 logarithm of *x*. This is usually more accurate
+ than ``log(x, 10)``.
.. function:: pow(x, y)