I know you can use
#show math.equation: set text(font: "Fira Math")
to affect all equations, but I just want to affect a single equation, can I change the font without using show?
For example using emptyset
$emptyset$ uses math font, but I want to use the Fira Math font, only for this equation, and not for the rest, is show
really required?
For example
#text(font:"Fira Math")[$emptyset$]
Doesn't work.
I want to rename the $emptyset$ into something like
#{
show math.equation: set text(font: "Fira Math")
[$emptyset$]
}
But I am not very successful.
What you wrote is the correct approach: a scoped show-set rule. If you have to reuse this pattern frequently, you can always define a helper function:
#let fonted-math(font: "Fira Math", body) = {
show math.text: set text(font: font)
body
}
#fonted-math[$emptyset$]
$emptyset$