Writing double-stroke letters like on a blackboard

Mathematicians need a lot of symbols for variables, constants, vectors, operators, sets, spaces, and many 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.

When writing on a blackboard or a whiteboard in a lecture, it’s challenging to write bold letters. So, double-stroke letters were invented. A typographer may prefer these, as they don’t destroy the grayness of 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:

   \[
     \mathds{N} \subset \mathds{Z} \subset
     \mathds{Q} \subset \mathds{R} \subset \mathds{C}
   \]

3. Compile; the output will be the following:

...