Because the Math have many technical symbols.
In the MathOverflow site if we text the
$\sin^2 \theta$ we can get the
So, if there is a open source editor we can use?
The notation you refer to originates in the Latex typesetting system which is open source. You might want to have a look into the various out-of-the-box solutions which exist for typesetting Latex documents. Miktex is a good starting point.