# Tikz picture of two mathematical functions

I'm trying to draw the functions y=(0.05*0.4+0.1*2*x)/(0.05+0.1*2) and x=-0.1/(2*10*(y - 0.1))+y, by using tikz as follows

\begin{tikzpicture}
\begin{axis}[xmin=0,xmax=1,ymin=0,ymax=1, samples=1000, xlabel={$c$}, ylabel={$s$}]
\addplot[blue, ultra thick] (x,(0.05*0.4+0.1*2*x)/(0.05+0.1*2));
\addplot[red,  ultra thick] (-0.1/(2*10*(x - 0.1))+x,x);
\end{axis}
\end{tikzpicture}


I obtained the picture: But I'm not sure about the result (tikz seems to have drawn also the asymptote of second function). For me (and Mathematica) the result should be instead the following: Can anybody tell me what's wrong with this picture and my tikz code?

• Add appropriate curly brackets: \addplot[blue, ultra thick] (x,{(0.05*0.4+0.1*2*x)/(0.05+0.1*2)}); \addplot[red, ultra thick] ({-0.1/(2*10*(x - 0.1))+x},x);. – user121799 Mar 16 at 18:18

## 1 Answer

The TikZ/pgfplots parser gets confused about the brackets, it does not know which of them are delimiters of coordinates or expressions in the functions. So you have to help them a bit by adding curly brackets.

\documentclass[tikz,border=3.14mm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.16}
\begin{document}
\begin{tikzpicture}
\begin{axis}[xmin=0,xmax=1,ymin=0,ymax=1, samples=1000, xlabel={$c$},
ylabel={$s$},unbounded coords=discard]
\addplot[blue, ultra thick] (x,{(0.05*0.4+0.1*2*x)/(0.05+0.1*2)});
\addplot[red,  ultra thick,domain=0:0.099] ({-0.1/(2*10*(x - 0.1))+x},x);
\addplot[red,  ultra thick,domain=0.11:1] ({-0.1/(2*10*(x - 0.1))+x},x);
\end{axis}
\end{tikzpicture}
\end{document} • Thank you! It's clear. Is there a way to remove the asymptote? – Mark Mar 16 at 20:05
• @Mark Sure. (Sorry, was offline.) I removed the red asymptote. If you want to remove the blue one as well, remove \addplot[blue, ultra thick] (x,{(0.05*0.4+0.1*2*x)/(0.05+0.1*2)});. The red one was because you plotted over a singularity at x=0.1, and one easy way to remove it is to add two separate plots that avoid it. – user121799 Mar 16 at 22:28