pgfplots:在 foreach 中使用 pi

pgfplots:在 foreach 中使用 pi

\foreach我怎样才能在a中使用 pi 这个数字pgfplots

\documentclass[tikz, dvipsnames]{standalone}
\usepackage{pgfplots}
\usepackage{mathtools}
\pgfplotsset{compat = 1.8}
\begin{document}
\begin{tikzpicture}
  \begin{axis}
    \foreach \v/\colo in {0/red, {pi/4}/blue, {pi/2}/orange, {3*pi/4}/green,
      {5*pi/4}/Purple, {3*pi/2}/Salmon, {7pi/4}/SeaGreen}{
      \expandafter\addplot\expandafter+\expandafter[\colo, domain = 0:2*pi]
      ({(exp(x) + exp(-x)) / 2 * cos(deg(\v))},
      {(exp(x) - exp(-x)) / 2 * sin(deg(\v))});
    }
  \end{axis}
\end{tikzpicture}
\end{document}

我想v成为pi但是

ERROR: Package PGF Math Error: Unknown operator `p' or `pi' (in '(exp(x) + exp(-x)\
) / 2 * cos(deg(7pi/4))').

答案1

{7pi/4}

应该有一个 *

{7*pi/4}

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