Plot only producing straight line

I need to plot the function y = sec(x)/exp(tan(x)) however the code I used (which I’ve pasted below) only produces a straight line.

begin{center}
begin{tikzpicture}
begin{axis}[xlabel={$x$},ylabel={$y$},
   axis equal,axis lines=middle,
   width=12cm,height=7cm,
   xmin=-1.6,xmax=1.6,
   ymin=-1,ymax=2,
   yticklabel=empty,xticklabel=empty,
   ytick=empty,xtick=empty]
addplot[color=red,domain=-1.57:1.57,samples=100] {sec(x)/(exp(tan(x))};
end{axis}
end{tikzpicture}
 end{center}

I’ve tried individual functions. exp(x) worked, but tan(x) and sec(x) both similarly returned a straight line. Any help or guidance would be greatly appreciated!

documentclass{article}
usepackage{tikz}
usepackage{pgfplots}

begin{document}

begin{center}
begin{tikzpicture}
begin{axis}[xlabel={$x$},ylabel={$y$},
   axis equal,axis lines=middle,
   width=12cm,height=7cm,
   xmin=-1.6,xmax=1.6,
   ymin=-1,ymax=2,
   yticklabel=empty,xticklabel=empty,
   ytick=empty,xtick=empty]
addplot[color=red,domain=-1.3:1.3,samples=100] {sec((x)r)/(exp(tan((x)r))};
end{axis}
end{tikzpicture}
 end{center}
 
end{document}