Plot of sin(x)/x is shifted/misplaced - latex

Question

I want to plot sin(x)/x but the x-axis is offset by \pi/2.
The mwe is
\documentclass{scrbook}
\usepackage{tikz,pgfplots}
\begin{document}
\begin{figure}
\centering
\begin{tikzpicture}
\begin{axis}[
% cycle list,
clip=true,
xmin=-4*pi,xmax=4*pi,
%axis lines=left,
%axis x line=middle,
%axis y line=left,
xtick distance = pi/2,
xticklabels={
% foo,
$-4\pi$,
$-\frac{7}{2}\pi$,
$-3\pi$,
$-\frac{5}{2}\pi$,
$-2\pi$,
$-\frac{3}{2}\pi$,
$-\pi$,
$-\frac{1}{2}\pi$,
$0$,
$\frac{1}{2}\pi$,
$\pi$,
$\frac{3}{2}\pi$,
$2\pi$,
$\frac{5}{2}\pi$,
$3\pi$,
$\frac{7}{2}\pi$,
$4\pi$
},
ylabel = {$\sin(x)/x$},
xlabel = {},
]
\addplot[
domain=-4*pi:4*pi,samples=4000,
]
{sin(deg(x))/deg(x)};
\end{axis}
\end{tikzpicture}
\caption{Example of local minima, and global minima and maxima.}
\label{fig:Example of local minima, and local and global maxima.}
\end{figure}
\end{document}
When I uncomment line 16 %foo the x-labels are misplaced, when I leave it there, the label foo is not printed but the alignment of the labels are (seemingly) correct.
I have no idea where the issue is.

Answer 1

Instead of manually adding the labels, you could use https://tex.stackexchange.com/a/396298/36296 (I had to increase the width of the graph, otherwise there wouldn't be enough room to label every pi/2):
\documentclass{scrbook}
\usepackage{tikz,pgfplots}
% Load math library, for \tikzmath
\usetikzlibrary{math}
\pgfplotsset{
% Typeset fractions of pi at regular intervals on x axis
x axis in pi/.style={
% Set tick distance from style argument
xtick distance={pi/#1},
% Set label style: calculate reduced fraction of pi
xticklabel={
\tikzmath{
% Calculate this tick's multiple of pi/#1
int \numorig, \gcd, \num, \denom, \absnum;
\numorig = round(\tick*#1/pi);
% Calculate reduced fraction for \numorig/#1
\gcd = gcd(\numorig,#1);
\num = \numorig / \gcd;
\absnum = abs(\num);
\denom = #1 / \gcd;
% Build label text
if \num < 0 then {
let \sign = -;
} else {
let \sign =;
};
if \absnum == 1 then {
let \numpi = \pi;
} else {
let \numpi = \absnum\pi;
};
if \denom == 1 then {
if \num == 0 then {
{ \strut$0$ };
} else {
{ \strut$\sign\numpi$ };
};
} else {
{ \strut$\sign\frac{\numpi}{\denom}$ };
% Other style with all pi symbols same and aligned:
%{ \strut$\sign\frac{\absnum}{\denom}\pi$ };
};
}
},
},
}
\begin{document}
\begin{figure}
\centering
\begin{tikzpicture}
\begin{axis}[
width=\textwidth,
% cycle list,
clip=true,
xmin=-4*pi,xmax=4*pi,
ylabel = {$\sin(x)/x$},
xlabel = {},
x axis in pi=2,
]
\addplot[
domain=-4*pi:4*pi,samples=4000,
]
{sin(deg(x))/deg(x)};
\end{axis}
\end{tikzpicture}
\caption{Example of local minima, and global minima and maxima.}
\label{fig:Example of local minima, and local and global maxima.}
\end{figure}
\end{document}