2. Compute the exterior derivatives of the following differential forms.

(a) x2 dy - y2 dx.

(b) sin(xy) dz dw + cos(zw) dx dy.

(

c) ...j x2 + y2 dy dz - ...j x2 + y2 dx dz.

(d) (eXY dz + eYZ dx)(sinxdy + cosydx).