XPath and math functionality

I would like to see trigonometric functions and similar but common
math functions built directly into XPath.  The reason for this is that 
I process Geography Markup Language data which contains real
numbers.  It is often a requirement when processing geographic
data that mathematical calculations are performed.   For example,
I recently wrote an XSLT 2.0 stylesheet containing functions to 
transform GML data from the Lambert Conformal Conic projection 
to decimal degrees, and vice versa.  These stylesheets heavily rely 
on java.lang.Math.  I am sure similar considerations would apply
when transforming GML into SVG for user interaction and display.

Having to rely on external language implementations makes stylesheets 
more difficult to write and less portable, which I assume is a goal of the
XPath language.