How to make formule bigger in org-mode of Emacs?

I found Org-mode + LaTeX to be a very wonderful tool. How can I alter the scale of formula? Currently it is too small for me. I know how to scale the Emacs font (C-x+), but this does not work for LaTeX formulas.

How can make the LaTeX formulae bigger in Org-mode?

I have tired to change some parameters, but the problem still remains.

Thank you for your patience!

Solution

According to the documentation

or (info "(org) Previewing LaTeX fragments")

You can customize the variable `org-format-latex-options' to
influence some aspects of the preview. In particular, the `:scale'
(and for HTML export, `:html-scale') property can be used to
adjust the size of the preview images.

A quick C-hvorg-format-latex-optionsRET gives us:

org-format-latex-options is a variable defined in `org.el'.
Its value is (:foreground default :background default :scale 1.0 :html-foreground "Black" :html-background "Transparent" :html-scale 1.0 :matchers
             ("begin" "$1" "$" "$$" "\\(" "\\["))


Documentation:
Options for creating images from LaTeX fragments.
[snip]
:scale       a scaling factor for the size of the images, to get more pixels
[snip]

For example, to set the scale to 2.0:

(setq org-format-latex-options (plist-put org-format-latex-options :scale 2.0))