Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
halve [hɑːv] vt (reduce) сокраща́ть (сократи́ть*perf) наполови́ну (divide) дели́ть*(раздели́ть*perf) попола́м
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.