We study the Cauchy singular integral operator $SwI$ on
$(-1,1)$, where $|w|$ is a generalized Jacobi weight.
This operator is considered in pairs of weighted spaces of
continuous functions, where the weights $u$ and $v$ are
generalized Jacobi weights with nonnegative exponents such
that $|w|=u/v$. We introduce a certain polynomial approximation
space which is well appropriated to serve as domain of
definition of $SwI$. A description of this space in terms of
smoothness properties shows that it can be viewed as a limit
case of weighted Besov spaces of continuous functions.
We use our results to characterize those of the operators
$awI+SbwI$ and $\varrho^{-1}(aw\varrho I+bSw\varrho I)$,
$\varrho^{-1}\in b^{-1}\Pi$, which act in certain pairs of
Ditzian-Totik type Besov spaces.
Keywords:
Cauchy singular integral operators,
Weighted spaces of continuous functions,
Approximation spaces