@article{oai:ynu.repo.nii.ac.jp:00006621, author = {Kaizuka, Tetsu}, issue = {2}, journal = {Yokohama Mathematical Journal = 横濱市立大學紀要. D部門, 数学}, month = {}, note = {application/pdf, In this paper we will discuss methods for the numerical solution of a single first-order ordinary differential equation $¥frac{dy}{dx}=f(x, y)¥equiv¥frac{Q(x,y)}{P(x,y)}$ with the initial condition $y(a)=b$ . To seek the solution, we often use Runge-Kutta method provided that $f(x, y)$ is continuous and satisfies Lipschitz condition $|f(x, y_{1})-f(x, y_{2})|¥leqq M|y_{1}-y_{2}|$ . If $P(x_{0}, y_{0})=0$ and $Q(x_{0}, y_{0})¥neq 0$ , then $ dyldx=¥infty$ , therefore we can not use Runge-Kutta method in the neighbourhood of $(x_{0}, y_{0})$ . Nevertheless, there often exists the solution. (ex. 1) In this case, putting $g(x, y)=¥frac{P(x,y)}{Q(x,y)}$ $g(x, y)$ often satisfies Lipschitz condition $|g(x_{1}, y)-g(x_{2}, y)|¥leqq M^{¥prime}|x_{1}-x_{2}|$ in the neighbourhood of $(x_{0}, y_{0})$ . Therefore, when we use Runge-kutta method provided with $P(x, y)^{2}+Q(x, y)^{2}¥neq 0$ , if $|P(x, y)|¥geqq|Q(x, y)|$ , we treat $y$ as the function of the independent variable $x$ , if $|P(x, y)|<|Q(x, y)|$ , we treat $x$ as the function of the independent variable $y$ , that is, if $|¥frac{dy}{dx}|¥leqq 1$ , then ¥frac{dy}{dx}=¥frac{Q(X_{1}y)}{P(X_{1}y)}$ , and if $|¥frac{dy}{dx}|>1$ , then $¥frac{dx}{dy}=¥frac{P(x,y)}{Q(X_{1}y)}$ , then, as $|dy/dx|$ and $|dx/dy|$ are both smaller than 1, the error of the increment will be smaller. If $P(x_{0}, y_{0})^{2}+Q(x_{0}, y_{0})^{2}=0$ , we must stop pursuing the solution at $(x_{0}, y_{0})$ as $(x_{0}, y_{0})$ is a singular point. (ex. $6¥sim ex$ . $11$ ) Furthermore, if we can find proper continuations between dyldx and dxldy, we can even pursue closed curves. (ex. 1)}, pages = {183--189}, title = {A REMARK ON THE NUMERICAL SOLUTION OF A SINGLE FIRST-ORDER ORDINARY DIFFERENTIAL EQUATION}, volume = {25}, year = {1977} }