What is the angle θ\thetaθ between the vectors u=(1,2,0)\mathbf{u} = (1, 2, 0)u=(1,2,0) and v=(2,1,0)\mathbf{v} = (2, 1, 0)v=(2,1,0)?
θ=0\theta = 0θ=0
θ=π4\theta = \frac{\pi}{4}θ=4π
θ=arccos(45)\theta = \arccos\left(\frac{4}{5}\right)θ=arccos(54)
θ=π2\theta = \frac{\pi}{2}θ=2π