Size of the integral sign

Is there any way to increase integral sign in math formula?
Another thing.I made shotcut on keyboard to open Math in Writer.
How can I insert the formula in text and close Math with keyboard, without left click with mouse on document?
Thank You and sorry for my English.

Thanks for your answer. That is actually very helpfull. Can’t believe I was so stupid about closing math window. Probably thought that I tried esc.

It’s fun to find LibreOffice capabilities I didn’t know about. I found this OpenOffice page showing a formula font size function. An example:

stack{t_max # size*3 int{} # t_min} exp(-k_1 cdot t)dt

You can close the formula window by hitting the ESC key.