import module namespace
math="http://www.zorba-xquery.com/modules/math";

math:slope((2, 3, 9, 1, 8, 7, 5), (6, 5, 11, 7, 5, 4, 4))


(:

Expected output:

<?xml version="1.0" encoding="UTF-8"?>
0.3055555555555556

                
:)