\begin{align} \frac{dy}{dx}=\frac{1}{x^2+y^2} \end{align}
The reference answer is $(-\infty,\infty)$,or $(-\infty,0)$ or$(0,\infty)$. I don't know how to deal with the origin.
\begin{align} \frac{dy}{dx}=\frac{1}{x^2+y^2} \end{align}
The reference answer is $(-\infty,\infty)$,or $(-\infty,0)$ or$(0,\infty)$. I don't know how to deal with the origin.