The issue: Does your browser handle Mathematical Markup Language (MathML) properly?
This math display in mathematical markup $${\int}_{0}^{\infty}{t}^{x}{e}^{t}\frac{dt}{t}\phantom{\rule{0.6em}{0ex}}=\phantom{\rule{0.6em}{0ex}}\frac{1}{x}\prod _{k=1}^{\infty}\frac{{\left(1+\frac{1}{k}\right)}^{x}}{\left(1+\frac{x}{k}\right)}$$ should, but for size, match the graphic image in the following display:
As to size, the mathematical markup display should expand and shrink in scale as you expand and shrink the fonts you are using, while the graphic image has a fixed size independent of browser font size or window size.
Check the radical in the following standard formula for the roots of the quadratic equation $a{x}^{2}+bx+c=0$: $$x=\frac{b\pm \sqrt{{b}^{2}4ac}}{2a}$$
This formula also should expand and shrink in scale as you adjust your fonts. If the radical is illformed, you will profit from acquiring additional fonts that you should be able to procure without cost.
Mathematicians and scientists also sometimes use exotic typefaces. Particularly, in the U.S. the use of
doublestruck (corresponding to “blackboard bold”) fonts
script (or “calligraphic”) fonts
Fraktur (or “Gothic”) fonts
is not infrequent.
The following table provides a quick check on whether your browser finds fonts in these families available:

The table above should render as shown in this graphic image
– which you may click to enlarge.
On this page the characters seeking these fonts are colorcoded as follows:

If you see colored but unstyled Roman letters in the table, you will also in this case profit from acquiring additional fonts that you should be able to procure without cost.