In this post, I will discuss a few options about the integral sign. A few codes can enhance the look of your integrals.

**|**$\int_a^b f(x) dx$ %

First we start with writing integral without any extra code. As you can see from the image, the integral sign will have nearly the text size, the limits will be very close to the function, and d for the derivative will be italic and will be seen as a variable.

**|**$\int_a^b f(x)\, \mathrm{d}x$

"\, " will seperate the function and the derivative part; and "\mathrm{d}" will enlight that d is not a variable, but the notation for differantial.

**|**$\int\limits_a^b f(x)\, \mathrm{d}x$

Next we keep the integral line same, but added "\limits" to move the limits of the integral to the top/bottom of the integral sign.

**|**\let\normalint\

**|**\def\int{\displaystyle\normalint}

Now, we will add these two lines of code before the "\begin{document}". Sadly, I cannot remember the source that I took this code from; but, still, thanks to the original writer.

**|**$\int_a^b f(x)\, \mathrm{d}x$

If we write the integral in a normal way; the sign of the integral will be larger than the text size.

**|**\let\normalint\

**|**\def\int{\displaystyle\normalint}

Again we keep these two lines of code before the "\begin{document}".

**|**$\int\limits_a^b f(x)\, \mathrm{d}x$

If we write the integral with the "limits".

Finally, I will give you an example of how I write an integral expression with evaluation part. I create the evaluate sign with "\bigg|".

Again we keep these two lines of code before the "\begin{document}".

**|**\let\normalint\**|**\def\int{\displaystyle\normalint}Again we keep these two lines of code before the "\begin{document}".

**|**$\int\limits_a^b f(x)\, \mathrm{d}x = \bigg|_a^b F(x)$