Program to create graph with modified bessel function $$e =\frac{1}{x}\frac{I_{1}(2x)}{I_{0}(2x)}$$
$$e =\frac{2}{1+\sqrt{1+x²\frac{8}{3}}}$$
$$e =\frac{1}{\sqrt{x\frac{4}{3}}} \frac{I_{\frac{2}{3}}(x\frac{4}{3}^{3/2})}{I_{\frac{-1}{3}}(x\frac{4}{3}^{3/2})}$$
I wanted to plot those functions but I'm having a hard time finding a program that does graphs with modified Bessel function of the first kind. Can anyone recommend me one? 

Have you tried Wolfram Alpha ? Just type Plot[BesselI(1,2x)/BesselI(0,2x)/x,{x,-5,5}] 
into the dialog box, and press Enter. If you want to plot more than one function at once, 
the syntax is Plot[{... , ... , ...},{x, ... , ...}], where the dots are to be replaced 
by the definitions of the functions, and the values of the horizontal plot limits.
