Include versionadded in (c)math.isfinite docs (thanks Ezio Melotti).  Other minor doc cleanups.
diff --git a/Doc/library/math.rst b/Doc/library/math.rst
index 22f6f5f..ec3955d 100644
--- a/Doc/library/math.rst
+++ b/Doc/library/math.rst
@@ -102,16 +102,18 @@
    Return ``True`` if *x* is neither an infinity nor a NaN, and
    ``False`` otherwise.  (Note that ``0.0`` *is* considered finite.)
 
+   .. versionadded:: 3.2
+
 
 .. function:: isinf(x)
 
-   Check if the float *x* is positive or negative infinity.
+   Return ``True`` if *x* is a positive or negative infinity, and
+   ``False`` otherwise.
 
 
 .. function:: isnan(x)
 
-   Check if the float *x* is a NaN (not a number).  For more information
-   on NaNs, see the IEEE 754 standards.
+   Return ``True`` if *x* is a NaN (not a number), and ``False`` otherwise.
 
 
 .. function:: ldexp(x, i)