Azimuthal unit vector
= Azimuthal unit vector
{title2=$\hat\phi=(-\sin\phi,\cos\phi,0)$}
The azimuthal <unit vector> is tangent to increasing <azimuthal angle> at fixed cylindrical radius and height. For $r>0$ it equals $(-y/r,x/r,0)$. A counterclockwise circle has tangent displacement $d\boldsymbol r=r\hat\phi\,d\phi$. Unlike a fixed Cartesian <basis vector>, its direction depends on position.