Include versionadded in (c)math.isfinite docs (thanks Ezio Melotti). Other minor doc cleanups.

Doc/library/cmath.rst

@@ -189,19 +189,22 @@ Classification functions
 
 .. function:: isfinite(x)
 
-   Return ``True`` if both the real and imaginary parts of *x* are finite,
-   and ``False`` otherwise.
+   Return ``True`` if both the real and imaginary parts of *x* are finite, and
+   ``False`` otherwise.
+
+   .. versionadded:: 3.2
 
 
 .. function:: isinf(x)
 
-   Return *True* if the real or the imaginary part of x is positive
-   or negative infinity.
+   Return ``True`` if either the real or the imaginary part of *x* is an
+   infinity, and ``False`` otherwise.
 
 
 .. function:: isnan(x)
 
-   Return *True* if the real or imaginary part of x is not a number (NaN).
+   Return ``True`` if either the real or the imaginary part of *x* is a NaN,
+   and ``False`` otherwise.
 
 
 Constants

Doc/library/math.rst

@@ -102,16 +102,18 @@ Number-theoretic and representation functions
    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)