[giac] fix tangent

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@28399 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Make sure Cubic does not throw error

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@28400 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Changing giac.js to the latest version in web/kickstart.xml

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@28401 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e