Cylindrical basis
= Cylindrical basis
{title2=$\mathbf e_r,\mathbf e_\theta,\mathbf e_z$}
The local <orthonormal basis> associated with <cylindrical coordinates>: $\mathbf e_r=(\cos\theta,\sin\theta,0)$, $\mathbf e_\theta=(-\sin\theta,\cos\theta,0)$, and $\mathbf e_z=(0,0,1)$. The first two <basis vectors> depend on the angular coordinate and are undefined on the axis without a choice of angle.