Vector Identiteis can be proven by grinding them out in component form, but it is more satisfying to use methods based on the integral theorems(Divergence, Stokes etc). Using both approaches, prove that following:
a) gradient X gradient(c) = 0 (i.e. curl of gradient of c = 0)
b) gradient • (gradient X A) = 0 (i.e. divergence of curl of A = 0)
where c and A are scalar and vector fields, respectively.