# Understanding a symbol

#### Petrus

##### Well-known member
Hello MHB,
I am reading about a rule which I got no clue what it's name is on english but I think that you Will understand.

My question is what do they mean with that $$\displaystyle D_g$$ and $$\displaystyle D_f$$

Regards,
$$\displaystyle |\pi\rangle$$

#### Klaas van Aarsen

##### MHB Seeker
Staff member
Re: Understanding a symbole

My question is what do they mean with that $$\displaystyle D_g$$ and $$\displaystyle D_f$$
Looks like $D_g$ means the domain of g.
That is the set of all values of x for which g(x) is defined.

#### Petrus

##### Well-known member
Re: Understanding a symbole

Looks like $D_g$ means the domain of g.
That is the set of all values of x for which g(x) is defined.
Thanks! That Was what I thought aswell! Thanks for taking your time!
Regards,
$$\displaystyle |\pi\rangle$$