




1. Suppose the surface is defined by z = x^{2} + y^{2},
and we use x and y as our parameters.
Then w = 2xi 2yj + k;
Its magnitude (used in the area measure), is (4x^{2}+4y^{2}
+1)^{1/2.}
2. Suppose the surface is defined by z = sinx siny and x and y are parameters.
Then w = cosx sinyi  sinx cosyj + k, and its magnitude
is (cos^{2}x sin^{2}y + sin^{2}xcos^{2}y + 1)^{1/2}.