Int (LaTeX symbol)

TeX has \int as the integral sign. Integral expressions are formed from the use of sub- and superscript, the judicious use of spacing, and simply writing out the differential. For example, a standard integral in LaTeX looks like

\int_a^b \! f(x) \, dx.

$\int _{a}^{b}\!f(x)\,dx.$

Note the use of \! to bring the function closer to the integral sign and the \, to push the differential farther away. Without them, the integral looks like

$\int_a^b f(x) dx,$

which, although looking similar, rankles the aesthetic sensibilites of many. Your use of spacing depends on your personal preference.

Examples

You can also treat the integral as a sum-class symbol with the \limit command. This is most useful for double and triple integrals. For example,

\iint\limits_D \, dx\,dy \quad \iiint\limits_E \, dx\,dy\,dz

$\iint \limits _{D}\,dx\,dy\quad \iiint \limits _{E}\,dx\,dy\,dz$

where D and E are regions that satisfy the requirements.

And let's not forget the closed path integral.

\oint \! \nabla f \, dt = 0

$\oint \!\nabla f\,dt=0$