Salix alba

I'm w:Salix alba on wikipedia.

A rotation matrix in block style <math display="block"> ...

$${\begin{pmatrix}\cos \theta &-\sin \theta \\\sin \theta &2\cos \theta \end{pmatrix}}$$

is the rotation matrix a reflection is in : style :<math>...

${\begin{pmatrix}\cos 2\theta &\sin 2\theta \\-\sin 2\theta &\cos 2\theta \end{pmatrix}}$

which is nice.

A display eqn

$${\begin{pmatrix}a&b\\c&d\end{pmatrix}}$$

with no preceeding newline

$$\int x\mathbf {d} x$$

foo now add a new line

$$\int y\mathbf {d} y$$

A pythagoren triple, inline $a^{2}+b^{2}=c^{2}$.