1.
Let a\vec{a} and b\vec{b} be two non-collinear unit vectors. If u=a(ab)b\vec{u} = \vec{a} - (\vec{a} \cdot \vec{b})\vec{b} and v=a×b\vec{v} = \vec{a} \times \vec{b}, then v|\vec{v}| is equal to