# draw graph showing the variations in distance in an intensity of light

How can I plot the function/graph below in the picture? My trial was not quite like what it should be \documentclass{standalone}
\usepackage{tikz}
\begin{tikzpicture}[scale=.6]
\draw[thick, smooth,samples=100,domain=-5.5:5.5] plot(\x,{0.5+1.0/(2.0*(\x))*sin((3*(\x))*180/pi)});
\end{tikzpicture}
\end{document}


Using general marmot logic, I would try something like this.

\documentclass[tikz,border=3.14mm]{standalone}
\begin{document}
\begin{tikzpicture}[scale=.6,declare function={
f(\x)=(1/(1+0.1*abs(\x)))*(cos((3*(\x))*180/pi)+1);}]
\draw[thick, smooth,samples=101,domain=-5.5:5.5]
plot(\x,{3*f(\x)});
\end{tikzpicture}
\end{document} This choice emerged from the observations that your plot shows a symmetric function whose local minima are all at the same y-value.

• If course, it is straightforward to add a grid, the axes and the other stuff, if needed. – user121799 Dec 31 '18 at 2:46
• \draw[->](-6.5,0)--(6.5,0); \draw[->] (0,-.8)--(0,7.5); \foreach\x in {-6, -5, ..., 5,6} \draw(\x, -.2)--(\x, .2); When this is added, how can I change the function so that the minimum points fit the points on the x-axis? – Thumbolt Dec 31 '18 at 4:38
• @Thumbolt declare function={f(\x)=(1/(1+0.1*abs(\x)))*(cos(\x*180)+1);} or declare function={f(\x)=(1/(1+0.1*abs(\x)))*(cos(\x*90)+1);}. – user121799 Dec 31 '18 at 4:43