I am trying to make math notation or infix expression from content mathml,
I am making help of ctop.xsl
for this:
/***ctop.xsl**/
Your input is incorrect, it should be in the MathML namespace:
<math xmlns="http://www.w3.org/1998/Math/MathML">
<apply><power></power><ci>x</ci><cn>2</cn></apply>
</math>
Not directly related to your problem but there is a newer, maintained, version of the ctop.xsl stylesheet here
https://github.com/davidcarlisle/web-xslt/tree/master/ctop