b Prove that u⋅(v×w)+v⋅(w×u)+w⋅(u×v)=3u⋅(v×w)\mathbf{u} \cdot (\mathbf{v} \times \mathbf{w}) + \mathbf{v} \cdot (\mathbf{w} \times \mathbf{u}) + \mathbf{w} \cdot (\mathbf{u} \times \mathbf{v}) = 3\mathbf{u} \cdot (\mathbf{v} \times \mathbf{w})u⋅(v×w)+v⋅(w×u)+w⋅(u×v)=3u⋅(v×w)