Rangers, on 50 points, have a game in hand on Celtic, on 52.
Kent opened the scoring in the "Old Firm" derby in the 36th minute when the unmarked winger latched on to Borna Barisic's low cross to whip his shot home, minutes after Ryan Christie's penalty for Celtic was saved by Allan McGregor.
Celtic equalised just before halftime when Callum McGregor's shot was deflected into the net off the arm of Odsonne Edouard.
However, Rangers reclaimed the lead in the 56th minute when Katic scored from a corner with a header at the near post.
Rangers lost forward Alfredo Morelos to a stoppage time red card - his seventh at the club in three seasons - when he received a second booking for a dive in the box.
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