# How to get this symbol (looks like a T or J)

I've tried drawing this symbol in Detexify, but with no luck:

It's not \mathcal{TJ}: $\mathcal{TJ}$ or \mathscr{TJ}: $\mathscr{TJ}$.

I'm guessing it's a T from context in the textbook. It has the same height as a capital letter.

How do I produce this symbol in mathjax (where I'm writing my textbook notes) and $\LaTeX$?

The symbol is a scipt uppercase T in math mode. The package euscript should fit your needs. Try

\documentclass[12pt]{article}
\usepackage{amsmath}
\usepackage[mathcal]{euscript}
\begin{document}
\begin{equation*}
\mathcal{T}
\end{equation*}
\end{document}


to obtain

Another very minimal example to obtain your symbol is:

\documentclass[a4paper,12pt]{article}
\usepackage{eucal}
\begin{document}
$\mathcal{T}$
\end{document}


As others have said, this is a calligraphic T in Euler script font. This font can also be loaded with the wonderful package mathalpha, which gives an easy way to use many calligraphic, script, fraktur and blackboard bold math fonts.

The Euler script font is associated to the \mathcal alphabet when loading mathalpha with option cal=euler. Here's a complete example.

\documentclass{article}
\usepackage[cal=euler]{mathalpha}
\begin{document}
$\mathcal{T}$
\end{document}