[Tex/LaTex] Small integral symbol

equationssymbols

I can't understand why an integral of a fraction doesn't resize the integral symbol by itself.

$\text{SAR}=\int_{campione}\dfrac{\bf{\sigma}(r)|\bf{E}(r)|^2}{\bf{\rho}(r)}dr$

enter image description here

I saw this Big integral sign but with bigints nothing changes (and yes, I loaded the package and I erased all those files that work like a cache). I wouldn't write an instruction to make this resize

Best Answer

You simply need

$\text{SAR}=\displaystyle\int_{\mathit{campione}}\dfrac{\bf{\sigma}(r)|\bf{E}(r)|^2}{\bf{\rho}(r)}\,dr$,

if it really is an inline, not displayed, math. If not, a solution may be as follows:

\[
\text{SAR}=\int_{\mathit{campione}}\dfrac{\bf{\sigma}(r)|\bf{E}(r)|^2}{\bf{\rho}(r)}\,dr
\]

Using \bf in LaTeX is not recommended. You have, e.g., \mathbf{}.