绘制非连续函数

Question

我正在尝试绘制此函数，但它应该在每个 k*pi 上趋于无穷大，但它甚至不像正确的图。我做错了什么吗？

\begin{tikzpicture}
\begin{axis}[
    axis lines = center,
    xmin=-2*pi,xmax=2*pi,
    xlabel = $x$,
    ylabel = {$g(x)$},
    xtick={0,1.57,3.14,4.71,6.28,-1.57,-3.14,-4.71,-6.28},
    xticklabels={$0$, $\frac{\pi}{2}$,$\pi$,$\frac{3}{2}\pi$,$2\pi$, $-\frac{\pi}{2}$,$-\pi$,$-\frac{3}{2}\pi$,$-2\pi$},
]
\addplot [
    domain=-10:10, 
    samples=100, 
    color=red,
]
{abs(((sin(deg(x+(pi/4))^2)/(cos(deg((x+(pi)/2)))))};
\end{axis} 
\end{tikzpicture}

它应该是这样的

Answer 1

欢迎！括号设置得有点不妥，我添加了unbounded coords=jump，还调整了域以适应xmin和max。结果看起来像目标屏幕截图。

\documentclass[tikz,border=3mm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.17}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
    axis lines = center,
    xmin=-2*pi,xmax=2*pi,
    xlabel = $x$,
    ylabel = {$g(x)$},
    xtick={0,1.57,3.14,4.71,6.28,-1.57,-3.14,-4.71,-6.28},
    xticklabels={$0$, $\frac{\pi}{2}$,$\pi$,$\frac{3}{2}\pi$,$2\pi$, $-\frac{\pi}{2}$,$-\pi$,$-\frac{3}{2}\pi$,$-2\pi$},
    unbounded coords=jump,ymax=5
]
\addplot [
    domain=-2*pi:2*pi, 
    samples=221, 
    color=red,
]
{abs(pow(sin(deg(x+pi/4)),2)/(cos(deg(x+pi/2))))};
\end{axis} 
\end{tikzpicture}
\end{document}

还请注意，此处发布的代码预计以 开头\documentclass并以 结尾\end{document}。

或者使用从-10到的域名10。

\documentclass[tikz,border=3.14mm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.17}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
    axis lines = center,
    xmin=-10,xmax=10,
    xlabel = $x$,
    ylabel = {$g(x)$},
    xtick={0,1.57,3.14,4.71,6.28,-1.57,-3.14,-4.71,-6.28},
    xticklabels={$0$, $\frac{\pi}{2}$,$\pi$,$\frac{3}{2}\pi$,$2\pi$, $-\frac{\pi}{2}$,$-\pi$,$-\frac{3}{2}\pi$,$-2\pi$},
    unbounded coords=jump,ymax=5
]
\addplot [
    domain=\pgfkeysvalueof{/pgfplots/xmin}:\pgfkeysvalueof{/pgfplots/xmax}, 
    samples=401, 
    color=red,
]
{abs(pow(sin(deg(x+pi/4)),2)/(cos(deg(x+pi/2))))};
\end{axis} 
\end{tikzpicture}
\end{document}

请注意，在选择时必须小心谨慎samples。