(a) Express $\tan^{-1}\left$ \frac{\cos x}{1 - \sin x} \right$$, where $-\frac{\pi}{2} < x < \frac{\pi}{2}$ in the simplest form. OR (b) Find the principal value of $\tan^{-1}(1) + \cos^{-1}\left$-\frac{1}{2}\right$ + \sin^{-1}\left$-\frac{1}{\sqrt{2}}\right$$.