Here is mine. Didn't look because I didn't want to write with a tainted mind, but it is pretty close to what is already here, if not exact. But a fun little exercise.
(defun FindSector ( rad sec / Sector)
(setq Sector (/ rad (/ (* 2 pi) sec)))
(if (equal (rem Sector 1) 0.0 0.000001)
Sector
(+ 0.5 (fix Sector))
)
)