Show that, for every choice of given angles $\theta, \phi$, and $\psi$, the following are unit vectors in the Euclidean norm: (a) $(\cos \theta \cos \phi, \cos \theta \sin \phi, \sin \theta)^T$.
(c) $(\cos \theta \cos \phi \cos \psi, \cos \theta \cos \phi \sin \psi, \cos \theta \sin \phi, \sin \theta)^T$.
(b) $\frac{1}{\sqrt{2}}(\cos \theta, \sin \theta, \cos \phi, \sin \phi)^T$.