Usually, the LaTeX is used to create documents and for these purposes you should setup MikTeX or another TeX system. If you want to create only the formula, then you should consider the type of problem to be solved. For sites with dynamic content, it is advisable to use a modules like MathJs, jsMath or online servises that provide the conversion (see http://www.codecogs.com/latex/eqneditor.php
In applications, the generation of formulas is rarely necessary.To display the formulas used images. If you need a good quality pictures use vector images. And if you create a control to display graphs, it is advisable to look for a ready-made solution from the Internet. By the way, to generate formulas the mimetex is not so huge.