$\text{ If }\sum _{\mathrm{i}=1}^{20} {\sin }^{-1}{\mathrm{x}}_{\mathrm{i}}=10\mathrm{\pi }\text{ then }\sum _{\mathrm{i}=1}^{20} {\mathrm{x}}_{\mathrm{i}}$ is equal to

$$\begin{gathered} \text{ Since }-\frac{\mathrm{\pi }}{2}\le {\sin }^{-1}{x}_{\mathrm{i}}\le \frac{\mathrm{\pi }}{2},\therefore {\sin }^{-1}{\mathrm{x}}_{\mathrm{i}}=\frac{\mathrm{\pi }}{2},1\le \mathrm{i}\le 20 \\ \therefore {\mathrm{x}}_{\mathrm{i}}=1,1\le \mathrm{i}\le 20\text{. Thus, }\sum _{\mathrm{i}=1}^{20} {\mathrm{x}}_{\mathrm{i}}=20. \end{gathered}$$