Value of the expression $\frac{\sin \theta}{1+\cos \theta}+\frac{\cos \theta}{1-\sin \theta}$ is
(a) $\sqrt{2} \sin \left(\frac{\pi}{4}+\theta\right)$
(b) $\sqrt{2} \cos \left(\frac{\pi}{4}-\theta\right)$
(c) $\sqrt{2} \sin \left(\frac{\pi}{4}-\theta\right)$
(d) $\sqrt{2} \cos \left(\frac{\pi}{4}+\theta\right)$