How to insert maths in google docs

1. http://thornahawk.unitedti.org/equationeditor/equationeditor.php
or
http://texify.com/links.php

2. input maths with latex gramma
For the first website, click right key of the mouse onto the image, "copy the image location";
For the second site, you can do it too, but at the end of the page, there is a short cut, just copy the address.

3. in google docs, click "insert"->"picture..."->"web", paste the web address.

Done.