Verify the Cauchy-Schwarz inequality for each of the following pairs of vectors $\mathbf{v}, \mathbf{w}$, using the standard dot product, and then determine the angle between them:
(a) $(1,2)^T,(-1,2)^T$,
(b) $(1,-1,0)^T,(-1,0,1)^T$,
(c) $(1,-1,0)^T,(2,2,2)^T$,
(d) $(1,-1,1,0)^T,(-2,0,-1,1)^T$,
(e) $(2,1,-2,-1)^T,(0,-1,2,-1)^T$.