Some MathJax frequently used here:
Equation in-line: \$123\$ \$\rightarrow\$ \$123\$
Equation centered on a separate line: $$123$$ \$\rightarrow\$ $$123$$
Fractions: 1/2 \$\rightarrow\$ \$\frac{1}{2}\$ \$\rightarrow\$ \$\frac{1}{2}\$
Bigger fractions: 1/2 \$\rightarrow\$ \$\dfrac{1}{2}\$ \$\rightarrow\$ \$\dfrac{1}{2}\$
Something enclosed by full parentheses: (1/2) \$\rightarrow\$ \$\left(\frac{1}{2}\right)\$ \$\rightarrow\$ \$\left(\frac{1}{2}\right)\$
Exponent: I^2 \$\rightarrow\$ \$I^2\$ \$\rightarrow\$ \$I^2\$
Exponent: e^-1 \$\rightarrow\$ \$e^{-1}\$ \$\rightarrow\$ \$e^{-1}\$
Subscript: t0 \$\rightarrow\$ \$t_0\$ \$\rightarrow\$ \$t_0\$
Removing the italics from previous: \$\rightarrow\$ \text{t}_0 \$\rightarrow\$ \$\text{t}_0\$
Square Root: sqrt(9) \$\rightarrow\$ \sqrt{9} \$\rightarrow\$ \$\sqrt{9}\$
Cubic Root: ? \$\rightarrow\$ \sqrt[3]{27} \$\rightarrow\$ \$\sqrt[3]{27}\$
Greek symbols: \$\rightarrow\$ \alpha \beta \delta \Delta \omega \Omega \rho \$\rightarrow\$ \$\alpha \beta \delta \Delta \omega \Omega \rho\$...
Comparisons: i < 5 \$\rightarrow\$ i\lt 5 \$\rightarrow\$ \$i\lt 5\$ ...
\neq \$\rightarrow \:\neq\quad\$
\approx \$\rightarrow \:\approx\quad\$
\simeq \$\rightarrow \:\simeq\quad\$
Operators: \times \$\rightarrow \:\times\quad\$
\pm \$\rightarrow \:\pm\quad\$
\cdot \$\rightarrow \:\cdot\quad\$
\oplus \$\rightarrow \:\oplus\quad\$
\infty \$\rightarrow \:\infty\quad\$
Trigonometry: sin(x) \$\rightarrow\$ \sin x \$\rightarrow\$ \$\sin x\$
Logs: nat log(n) \$\rightarrow\$ \ln x \$\rightarrow\$ \$\ln x\$ ...
\log_{20}(x) \$\rightarrow \:\log_{20}(x)\quad\$
Sum: \sum_{a=1} ^{B} c \$\rightarrow \sum_{a=1} ^{B} c\$
Product: \prod_{a=1} ^{B} c \$\rightarrow \prod_{a=1} ^{B} c\$
Integral: \int_{0} ^{\infty} x dx \$\rightarrow \int_{0} ^{\infty} x dx\$
Limit: \lim_{x \to \infty} \$\rightarrow \lim_{x \to \infty}\$
Overline: /nRESET \$\rightarrow\$ \overline{\text{nRESET}} \$\rightarrow\$ \$\overline{\text{nRESET}}\$
Vector: \vec{x} \$\rightarrow\$ \$\vec{x}\$ also \overrightarrow{x} \$\rightarrow\$ \$\overrightarrow{x}\$