Writing double stroke letters as if on a blackboard

Mathematicians need a lot of symbols for variables, constants, vectors, operators, sets, spaces, and a lot of other objects. So they use small and big Latin and Greek letters, calligraphic letters, or write upright, italic, or bold so that they can be distinguished from each other in the same document.

In a lecture, when writing on a blackboard or a whiteboard, it is difficult to write bold letters. So, double stroke letters showed up. Well, in our documents, we still can simply switch to bold, on the other hand double stroke letters for number systems are already very common. Furthermore, a typographer may like this, since it doesn't destroy the grayness of a text, in contrast to bold symbols.

How to do it...

We will use the dsfont package. Follow these steps to get double stroke letters:

1. Load the dsfont package:

   \usepackage{dsfont}

2. In your document, use the \mathds command:

   \[
     \mathds{N} \subset \mathds{Z} \subset
     \mathds{Q} \subset \mathds...