自用的markdown与latex特殊符号

\triangleq
\approx
\xlongequal[y=\arctan x]{x=\tan y}
\sum_{\substack{j=1 \\ j\neq i}}
\iiint\limits_\Omega
\overset{\circ}{\vec{r}}
\varphi
\checkmark
\stackrel{\cdot\cdot\cdot}{x}

$$\triangleq \approx \underset{y=\arctan x}{\overset{x=\tan y}{}}\sum _{\begin{array}{c}j=1\\ j\ne i\end{array}}\underset{\Omega }{\iiint }\stackrel{\circ }{r}\phi ✓\stackrel{\cdot \cdot \cdot }{x}$$
$\text{LATEX}$ Mathematical Symbols
List of LaTeX mathematical symbols -oeis
List of Greek letters and math symbols -overleaf