Angular displacement is defined as the ratio of length and radius.
Angular displacement= Length/Radius
Now we know
Dimensional Formula of Length = M0L1T0
Dimensional Formula of Radius = M0L1T0 —- Radius is related to length.
So
Angular displacement= M0L1T0/M0L1T0
Hence Dimensional Formula of Angular displacement = M0L0T0
SI units of Angular displacement is radian