*** QuickLaTeX cannot compile formula: \begin{array}{l} \frac{d y}{d x}+\sqrt{\frac{1-y^{2}}{1-x^{2}}}=0 *** Error message: \begin{array} on input line 8 ended by \end{document}. leading text: \end{document} Improper \prevdepth. leading text: \end{document} Missing } inserted. leading text: \end{document} Missing \cr inserted. leading text: \end{document} Missing $ inserted. leading text: \end{document} You can't use `\end' in internal vertical mode. leading text: \end{document} \begin{array} on input line 8 ended by \end{document}. leading text: \end{document} Missing } inserted. leading text: \end{document} Emergency stop.