In the question Different Font in a Math Environment, the answer does not explain how to change the math font, but how to change the text font (leaving the math the same). Is there a way to change the math font, keeping the text as is?
euler package does that for instance, but mixing it with the default Computer Modern text fonts does not look good. Indeed, the Euler fonts were meant to be originally used with the Concrete fonts.
You really need to choose both kinds of fonts at the same time so they match. See A Survey of Free Math Fonts for TeX and LaTeX for several examples.