of arc
https://doi.org/10.1351/goldbook.D01560
Non-SI unit of plane angle, 1 =π180 rad0.017 453 29...rad.
Sources:
Green Book, 2nd ed., p. 113 [Terms] [Book]
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 968 [Terms] [Paper]