Hi,
let say I have a function as following
sin x approx 0.866
Is there any way I can change the size of the symbol - approx? Thank you.
You can change for this character the font size or use a different font.
Concerning fonts please have a look here: Where do I download Libre font sets? I don't see a link on Libre.com
I also recommend to look at the fonts indicated by @rautemiekka
Be always careful with license rights.