$\begin{aligned} & \quad \text { If } y=\sqrt{\mathrm{f}(x)+\sqrt{\mathrm{f}(x)+\sqrt{\mathrm{f}(x)+\ldots}}}, \text { then } \frac{\mathrm{d} y}{\mathrm{~d} x}=\frac{\mathrm{f}^{\prime}(x)}{2 y-1} \\ & \quad y=\sqrt{(x-\sin x)+\sqrt{(x-\sin x)+\sqrt{(x-\sin x)+\ldots}}} \\ & \therefore \quad \frac{\mathrm{d} y}{\mathrm{~d} x}=\frac{1-\cos x}{2 y-1}\end{aligned}$