Update demo_tnt-elements.py

Author: jmv2009

python/demo/demo_tnt-elements.py

@@ -225,7 +225,7 @@ def create_tnt_quad(degree):
             basix.CellType.quadrilateral, basix.PolynomialType.legendre, degree-2, 2, pts
         )
         # this assumes the conventional [0 to 1][0 to 1] domain of the reference element, 
-        # and takes the Laplacian of (1-u)*u*(1-v)*v*poly, 
+        # and takes the Laplacian of (1-u)*u*(1-v)*v*pol_set[0], 
         # cf https://github.com/mscroggs/symfem/blob/main/symfem/elements/tnt.py
         poly = (pol_set[5]+pol_set[3])*(u-1)*u*(v-1)*v+ \
                 2*(pol_set[2]*(u-1)*u*(2*v-1)+pol_set[1]*(v-1)*v*(2*u-1)+ \