overlay latex on vector image

You can use overpic:

\documentclass{article}
\usepackage{graphicx,xcolor}
\usepackage{overpic}

\begin{document}
\begin{overpic}[percent,width=6cm]{example-image.pdf}
  \put(60,10){%
    \makebox(0,0)[lb]{%
      \fontsize{12}{14.4}\normalfont
      \color{red!80}$\displaystyle\int_0^1 f(x)\,dx$%
    }%
  }%
\end{overpic}

\end{document}

Here is a way to do it with Tikz:

Tikz primer

Within LaTeX you can insert a tikzpicture environment.

Within it you can place \nodes: consider them as boxes or labels you can place with (almost) any LaTeX content.

A \node can have:

• options in [ ]
• a name, like (A)
• a specified position
• LaTeX content inside { }
• end such statements by ;

The most important one for you will just include your image, like so: \node (A) {\includegraphics{example-image}};

Several ways to place nodes

Node (A), the image is placed without a coordinate. So A's center by default is at (0,0).

Node (a) in red is also placed implicitely at the default (0,0), and is hard to read from the images label.

Node (b) in teal is placed top left (north west) of A, AND its own reference point is moved from the default ccnter to top left (north west), so it's displayed inside the image. The option to know is anchor.

Node (c) in orange is similar but placed at the intersection of the outer shape with a 110 deg beam from the center. To better see this I also drew the nodes shape in brown. The overlap to the outside is (probably) caused by the non-zero inner sep otpion. You also see, how to manipulate font size, if needed. // The \draw statement just shows the situation.

You also could use xshift and yshift, if that's more convenient, instead of guessing an angle.

Node (d) in magenta shows some absolute placement. While the variants above are usedul, if you don't know or don't care about the images dimensions, here you certaibly need to know them.

Node (e) in blue is ismilar, but uses polar coordinates to place this nodes center. (Often it's more convenient to place west, north west etc. of the node: use anchor in this situation.)

Finally, if you named relevant nodes, it's simple to add e.g. text as needed, here relative to node (d).

For tutorials and all options kindly check the Tikz manual, e.g. in this online version.

Code

\documentclass[10pt,border=3.1mm,tikz]{standalone}  % adjust border
\usepackage{graphicx}

\begin{document}
  \begin{tikzpicture}[  
  ]
    % ~~~ showing the image ~~~~~~~~~~~~~~~~~~~~~~~~
    \node (A) {\includegraphics{example-image}};    % looks for .pdf
    
    % ~~~ various ways to put math ~~~~~~~~~
    \node[red] (a) {$\int_0^1 f(x)dx$};             % at default (0,0)
    
    \node[teal,anchor=north west] (b) 
                                at (A.north west) 
                                {$\int_0^1 f(x)dx$};% at top left
    
    \node[orange,draw=brown,                        % shows shape
          anchor=north west,
          font=\huge]           (c) 
                                at (A.110) 
                                {$\int_0^1 f(x)dx$};% at top left
    \draw [draw=orange] (0,0) -- (A.110);           % showing 110 deg
    
    \node[magenta] (d) at (-3,-2) {$\int_0^1 f(x)dx$};  % at default (-3,-2)
    \node[blue   ] (e) at (-30:4) {$\int_0^1 f(x)dx$};  % polar coordinates
    
    % ~~~  if you need to do more, e.g. ~~~~~~~~~~~~~
    \node[anchor=north] at (d.south) {this shows, that \dots};

  \end{tikzpicture}
\end{document}