我在绘制 Cornu 螺旋时哪里失败了？

Question

\documentclass[border=20pt]{standalone}
\usepackage{pstricks-add}
\begin{document}
\psset{unit=5}
\begin{pspicture}[linewidth=1.2pt,algebraic](-1,-1)(1,1)
\psgrid[subgriddiv=5](-1,-1)(1,1)
\psplotDiffEqn[whichabs=0,whichord=1,plotpoints=900]{0}{8}{0 0}{cos(Pi*x^2/2)|sin(Pi*x^2/2)}
\psplotDiffEqn[whichabs=0,whichord=1,plotpoints=900]{0}{-8}{0 0}{cos(Pi*x^2/2)|sin(Pi*x^2/2)}
\rput(0.505,0.5){\color{red} $+$}
\rput(-0.505,-0.5){\color{red} $+$}
\end{pspicture}
\end{document}

但是，当我看到https://en.m.wikipedia.org/wiki/Euler_spiral?fbclid=IwAR35IhCPv5A56yeLvVWqgmZq_dlIX-EEH5C_aMdLj-I8og8k0AKGSroNUxU

如何修复？

Answer 1

这是两个不同的方程！

\documentclass[border=20pt]{standalone}
\usepackage{pstricks-add}
\begin{document}
\psset{unit=5}
\begin{pspicture}[linewidth=1.2pt,algebraic](-1,-1)(1,1)
\psgrid[subgriddiv=5](-1,-1)(1,1)
\psset{linecolor=blue}
\psplotDiffEqn[whichabs=0,whichord=1,plotpoints=900]{0}{8}{0 0}{cos(x^2)|sin(x^2)}
\psplotDiffEqn[whichabs=0,whichord=1,plotpoints=900]{0}{-8}{0 0}{cos(x^2)|sin(x^2)}
\psdots[dotscale=2,linecolor=red,dotstyle=+](! Pi 2 div sqrt 2 div dup)%
       (! Pi 2 div sqrt -2 div dup)
\end{pspicture}
\end{document}

你会得到相同的结果...但它有它的固定点不是在 P(-0.5,-0.5) 和 P(0.5,0.5) 中