I'm a newbie at Mathematica and I couldn't find how to label the maximum and the zero of a simple function in Plot with their names:
rho[r_] = 1 - r^2; Plot[rho[r], {r, -1, 1}, AxesLabel -> {r, \[Rho]}] and i want to show the maximum on the plot with
Subscript[\[Rho], c] and the point rho[1] with
Subscript[R, TF] How about:
rho[r_] = 1 - r^2; pl = Plot[rho[r], {r, -1, 1}, AxesLabel -> {r, \[Rho]}]; then
Show[{pl, Graphics[Text[Subscript[\[Rho], c], {0.05, 1.05}]], Graphics[Text[Subscript[R, TF], {1.05, 0.05}]]}, PlotRange -> All] 
You can put Text and Point on a plot with Epilog.
Plot[rho[r - Pi], {r, 1, 5}, AxesLabel -> {r, \[Rho]}, Epilog -> { PointSize[.01], Red, Point[zero], Black, Point[max], Map[Text[#[[1]], #[[2]], {0, -2}] &, Transpose[{{-Subscript["R", "TF"], Subscript["R", "TF"], Subscript["\[Rho]", "c"]}, Join[zero, {max}]}]]}, PlotRange -> All, PlotRangePadding -> .5] 
Calculated maximum and zeroes:
max = {r /. Last@#, First@#} &[FindMaximum[rho[r - Pi], r]] {3.14159, 1.} zero = {r, 0} /. NSolve[rho[r - Pi] == 0, r] {{2.14159, 0}, {4.14159, 0}} Using my answer to this question, you can generate any of the following interactively:
The only change needed is to remove the "String" in
InputField[Dynamic[lbl1[[#]]],String] and
InputField[Dynamic[lbl2[[#]]],String] to be able to type expressions.
The interactive interface looks like this:
Text[]orInset[]. $\endgroup$