I would like to write the following for the legend of a curve :

$$ \theta_n = \frac{\pi}{2}$$

However, when I write this in mathematica :

    Style["\[Theta]n=" <> ToString[Pi/2]]

The fraction goes under the $\theta_n$ like on this picture :

[![enter image description here][1]][1]

How can I do to make mathematica write properly what I want ? I am looking for a very simple solution.

  [1]: https://i.sstatic.net/SNlyX.png