two $\TeX$/$\LaTeX$ web service sites:
http://www.codecogs.com/components/equationeditor/equationeditor.php?lang=en-en
http://www.mathtran.org/

a group blog of several well-known scientists:
http://cosmicvariance.com/

## & test

$1+sin^2(x)$
$\mathfrak{Happy}\; \mathfrak{New }\;\mathfrak{Year! }$
$1+sin^2(x)$
$e^x$
$\int_M d\omega=\int_{\partial M}\omega$
$\begin{picture}(200,200)(0,0)\multiput(0,0)(50,0){5}{\line(0,1){200}}\multiput( 0,0)(0,50){5}{\line(1,0){200}}\end{picture}$
$\begin{picture}(100,100)(0,0) \put(0,0){\circle{3}} \put(0,0){\line(1,0){100}} \put(0,0){\line(0,1){100}} \put(100,100){\circle{3}} \put(50,10){\circle{3}} \put(55,15){{\bf test} label}\end{picture}$
$\begin{picture}(200,200)(0,0)\multiput(0,0)(40,10){5}{\line(1,4){40}}\multiput( 0,0)(10,40){5}{\line(4,1){160}}\end{picture}$
$$\nabla \times \,A = \frac{1}{{rsin\theta }}\left[ {\frac{{\partial (A_\phi sin\theta )}}{{\partial \theta }} - \frac{{\partial A_\theta }}{{\partial \phi }}} \right]\hat r + \frac{1}{r}\left[ {\frac{1}{{sin\theta }}\frac{{\partial A_r }}{{\partial \phi }} - \frac{{\partial (rA_\phi )}}{{\partial r}}} \right]\hat \theta + \frac{1}{r}\left[ {\frac{{\partial (rA_\theta )}}{{\partial r}} - \frac{{\partial A_r }}{{\partial \theta }}} \right]\hat \phi$$
$$\nabla \times A = \left( {\frac{{\partial A_z }}{{\partial y}} - \frac{{\partial A_y }}{{\partial z}}} \right)i + \left( {\frac{{\partial A_x }}{{\partial z}} - \frac{{\partial A_z }}{{\partial x}}} \right)j + \left( {\frac{{\partial A_y }}{{\partial x}} - \frac{{\partial A_x }}{{\partial y}}} \right)k$$
$\textcolor{red}{Test}\begin{picture}(200,200)(0,0)\put(50,50){\textcolor{green}{\line(1,1){50}}}\end{picture}$
$\]\begin{picture}(200,200)(0,0)\multiput(0,0)(40,10){5}{\line(1,4){40}}\multiput(0,0)(10,40){5}{\line(4,1){160}}\put(0,0){\vector(1,4){170}}\put(50,50){\circle*{10}}\put(160,40){\framebox(80,40)[r]{\textcolor{blue}{\bf $x_{Bob}$ } } }\put(40,160){\textcolor{yellow}{\dashbox(80,40)[t]{\textcolor{red}{ $t_{Bob}$ } }}}\qbezier(100,100)(200,100)(200,200)\linethickness{8pt}\textcolor{green}{\qbezier(0,0)(0,100)(100,100)}\linethickness{1pt}\qbezier(0,0)(0,100)(100,100)\end{picture}\[$

## test:

The LaTeX expression: “\sqrt(3){ 1 + x^2 }” will not work correctly with : , use “\root 3 \of { 1 + x^2 }” instead: .

The LaTeX expression: “\matrix {a & b \cr c & d }” will not work correctly with : , use “\left[ \matrix {a & b \cr c & d} \right]” instead: .