Fix capitalization.

Doc/library/decimal.rst

@@ -1717,7 +1717,7 @@ to work with the :class:`Decimal` class::
    def cos(x):
        """Return the cosine of x as measured in radians.
 
-       The taylor series approximation works best for a small value of x.
+       The Taylor series approximation works best for a small value of x.
        For larger values, first compute x = x % (2 * pi).
 
        >>> print(cos(Decimal('0.5')))
@@ -1743,7 +1743,7 @@ to work with the :class:`Decimal` class::
    def sin(x):
        """Return the sine of x as measured in radians.
 
-       The taylor series approximation works best for a small value of x.
+       The Taylor series approximation works best for a small value of x.
        For larger values, first compute x = x % (2 * pi).
 
        >>> print(sin(Decimal('0.5')))