I would like to highlight a result in this way. How can I do that?

Question

\documentclass[11pt,spanish]{article}
\usepackage[utf8]{inputenc}
\usepackage[spanish]{babel}
\usepackage{graphicx}
\usepackage{amsmath,amssymb}
\oddsidemargin=-0.5cm
\textwidth=17.4cm 
\textheight=48\baselineskip 
\topmargin=-1.5cm \setlength{\headheight}{40.53337pt}
\parindent 0pt 
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
\draw[help lines] (0,0) grid (2,2);
\pgftext[base] {$a_{\rho}=\frac{v^2}{\rho}$};
\color{orange}
\draw (0,0) -- (2,0);
\draw (2,2) -- (2,0);
\draw (1,-.25) -- (2.25,1);
\draw (1,-.5) -- (2.5,1);
\draw (1,-.5) -- (2.5,1);

\end{tikzpicture}
\end{document}

This is my best try.

Answer 1

Depending on how you plan to use this, you could use the following:

But this will not work, for example, inside an align environment (assuming you want the = to be your alignment character).

Here is the code that produced the above image:

\documentclass{article}

\usepackage{tikz, amsmath}

\newcommand{\highlight}[2][orange!70]{\tikz[baseline, anchor=base]{\node[inner sep=2mm](A){$#2$};
    \draw[very thick, #1] (A.north east)--(A.south east)--(A.south west);
    \draw[thick, #1] ([shift={(.1,.5)}]A.south east)--([shift={(-.5,-.1)}]A.south east);
    \draw[#1] ([shift={(.1,.3)}]A.south east)--([shift={(-.3,-.1)}]A.south east);
}}

\begin{document}

\highlight{a_{\rho}=\dfrac{V^2}{\rho}}

\end{document}

There is an optional argument so you can easily change the highlight color:

\highlight[red!60]{a_{\rho}=\dfrac{V^2}{\rho}}

Here is a version you could use in an align environment. It uses tikzmark and requires naming a tikzmarknode at the beginning and another at the end. After the align environment, call the \highlight macro with the nodes you named.

You must compile twice.

\documentclass{article}

\usepackage{tikz, amsmath}
\usetikzlibrary{tikzmark}

\newcommand{\highlight}[3][orange!70]{\tikz[remember picture, overlay]{
    \draw[very thick, shorten >=-3mm, #1] ([shift={(.2,.1)}]#3.north east)--([shift={(.2,-.2)}]#3.south east)--([shift={(.2,-.2)}]#3.south east-|#2.west);
    \draw[thick, #1] ([shift={(.3,.3)}]#3.south east)--([shift={(-.3,-.3)}]#3.south east);
    \draw[#1] ([shift={(.3,.1)}]#3.south east)--([shift={(-.1,-.3)}]#3.south east);
}}

\begin{document}

\begin{align*}
x&=1\\
y&=2\\
\tikzmarknode{A}{a_{\rho}}&=\tikzmarknode{B}{\dfrac{V^2}{\rho}}
\end{align*}
\highlight{A}{B}

\end{document