Theorem and proof environments

[2017-09-12 Tue]

Here is a nice idea from Dr Z.ac, the blog of Zachary Harmany which I'm planning to use to enhance the mathematical usability of my blog.

In org-mode you can create theorem/proof-like environments as follows:

#+BEGIN_thm
Let $X$ be a compact space and $Y$ be a Hausdorff space. Any continuous
bijection $F\colon X\to Y$ is a homeomorphism.
#+END_thm
#+BEGIN_proof
It suffices to show that the image of a closed set $V\subset X$ is closed.
A closed set of a compact space is compact,
and the continuous image of a compact set is compact,
hence $F(V)$ is compact.
A compact subset of a Hausdorff space is closed,
therefore $F(V)$ is closed.
#+END_proof

When you export to LaTeX this will produce theorem and proof environments as usual. When you export to HTML, it will create a div tag of class "Theorem". Here's how to use CSS to style this so that it actually has an appropriate "Theorem" label (and end-of-proof symbol).

.thm{
    display:block;
    margin-left:10px;
    margin-bottom:20px;
    font-style:normal;
}
.thm:before{
    content:"Theorem.\00a0\00a0";
    float:left;
    font-weight:bold;
}

.proof{
    display:block;
    margin-left:10px;
    margin-bottom:30px;
    font-style:normal;
}
.proof:before{
    content:'Proof.\00a0\00a0';
    float:left;
    font-weight:bold;
}
.proof:after{
    content:"\25FC";
    float:right;
}

to get: