u\mathbf{u}
v\mathbf{v}
u=4.5\lVert \mathbf{u} \rVert = 4.5
v=4.5\lVert \mathbf{v} \rVert = 4.5
cosθ=0\cos \theta = 0
uv=0\mathbf{u} \cdot \mathbf{v} = 0