$\lim_{x \to +\infty} f(x)$
integral \[ \int_{a}^{b} x^2 \,dx \]
Inside text: $\sum_{n=1}^{\infty} 2^{-n} = 1$ On its own line: $$\sum_{n=1}^{\infty} 2^{-n} = 1$$
$\int_0^{2a}{\cos(x)dx}$