Correct option D. 4
Explanation:
tan9° – tan27° – tan63° + tan81°
Or (tan9° + tan81° ) – (tan27°+ tan63° )
Or (tan9° + cot9°)– (tan27° + cot27°)
or (sin92 + cos92)/(sin9°cos9°) - [(sin272 + cos272)/(cos27°sin27°)]
or 2/(2sin9°cos9°) - 2/(2sin27°cos27°)
or 2/sin18° - 2/sin54°
or (2 x 2cos36°sin18°)/sin18°sin54°) = (2 x 2cos36°)/cos36° = 4