Import

Hi, i download all extensions, but when i put :
<xsl:stylesheet version="1.0"
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:math="http://exslt.org/math"
                xmlns:func="http://exslt.org/functions"
                extension-element-prefixes="math">
<xsl:import href="math.xsl"/>
<xsl:output media-type="text/html"/>
Show me an error like "misplaced literal result in a func:function
container."

Can you help me?