Which of the following is the principal value branch of

    \[\mathbf{cose}{{\mathbf{c}}^{-\mathbf{1}}}~\mathbf{x}\]

? (a)

    \[\left( -\mathbf{\pi }/\mathbf{2},\text{ }\mathbf{\pi }/\mathbf{2} \right)\]

(b)

    \[\left[ \mathbf{0},\text{ }\mathbf{\pi } \right]\text{ }\text{ }\left\{ \mathbf{\pi }/\mathbf{2} \right\}\]

(c)

    \[\left[ -\mathbf{\pi }/\mathbf{2},\text{ }\mathbf{\pi }/\mathbf{2} \right]\]

(d)

    \[\left[ -\mathbf{\pi }/\mathbf{2},\text{ }\mathbf{\pi }/\mathbf{2} \right]\text{ }\text{ }\left\{ \mathbf{0} \right\}\]