Btukfyl

I am trying to a fancy theorem type for my notes. I like tcolorbox examples. But the one that I like most is giving me an error.

    Missing endcsname inserted.

This one is on page 360 of the tcolorbox manual. I do not understand why I am getting this error and how to fix. There was a similar question

https://tex.stackexchange.com/questions/174017/compile-error-missing-endcsname-inserted-with-code-and-tcolorbox

But it did not solve my problem. The result should be like this

I have added the code below. Please help me.

    documentclass[11pt]{article}

    usepackage{varioref}

    usepackage{cleveref}

    tcbuselibrary{skins}



    newtcbtheorem[use counter from=Definition]{YetAnotherTheorem}{Theorem}%

      {theorem style=change apart,enhanced,arc=0mm,outer arc=0mm,

      boxrule=0mm,toprule=1mm,bottomrule=1mm,left=1mm,right=1mm,

      titlerule=0mm,toptitle=0mm,bottomtitle=1mm,top=0mm,

      colframe=red!50!black,colback=red!5!white,coltitle=red!50!black,

      title style={top color=yellow!50!white,bottom color=red!5!white,

        middle color=yellow!50!white},

      fonttitle=bfseriessffamilynormalsize,fontupper=normalsizeitshape,

      }{theo}





    begin{document}

    begin{YetAnotherTheorem}{Mittelwertsatz f"{u}r $n$ Variable}{mittelwertsatz_n2}% Es sei $ninmathbb{N}$, $Dsubseteqmathbb{R}^n$ eine offene Menge und

    $fin C^{1}(D,mathbb{R})$. Dann gibt es auf jeder Strecke

    $[x_0,x]subset D$ einen Punkt $xiin[x_0,x]$, so dass gilt

      begin{equation*}

      f(x)-f(x_0) = operatorname{grad} f(xi)^{top}(x-x_0)

      end{equation*}

    end{YetAnotherTheorem}



    end{document}

This is too long for a comment. You have several issues:

• you are not loading tcolorbox package


• you need to add tcbuselibrary{theorems}
  


• you have not defined mathbb
  


• the use counter from=Definition does not work because you have not defined a definition environment. I am guessing that this is OK in your real document but below I replace this with number within=section.

The following code compiles and perhaps does what you want:

documentclass[11pt]{article}

usepackage{amssymb}

usepackage{varioref}

usepackage{tcolorbox}

tcbuselibrary{skins,theorems}

usepackage{cleveref}



newtcbtheorem[number within=section]{YetAnotherTheorem}{Theorem}%

  {theorem style=change apart,enhanced,arc=0mm,outer arc=0mm,

  boxrule=0mm,toprule=1mm,bottomrule=1mm,left=1mm,right=1mm,

  titlerule=0mm,toptitle=0mm,bottomtitle=1mm,top=0mm,

  colframe=red!50!black,colback=red!5!white,coltitle=red!50!black,

  title style={top color=yellow!50!white,bottom color=red!5!white,

    middle color=yellow!50!white},

  fonttitle=bfseriessffamilynormalsize,fontupper=normalsizeitshape,

  }{theo}



begin{document}



  begin{YetAnotherTheorem}{Mittelwertsatz f"{u}r $n$ Variable}{mittelwertsatz_n2}% Es sei $ninmathbb{N}$, $Dsubseteqmathbb{R}^n$ eine offene Menge und

  $fin C^{1}(D,mathbb{R})$. Dann gibt es auf jeder Strecke

  $[x_0,x]subset D$ einen Punkt $xiin[x_0,x]$, so dass gilt

    begin{equation*}

    f(x)-f(x_0) = operatorname{grad} f(xi)^{top}(x-x_0)

    end{equation*}

  end{YetAnotherTheorem}



end{document}

The output is: