${d \over {dx}}\left( {{1 \over {{x^4}\sec x}}} \right) = $

  • A
    ${{x\sin x + 4\cos x} \over {{x^5}}}$
  • B
    ${{ - (x\sin x + 4\cos x)} \over {{x^5}}}$
  • C
    ${{4\cos x - x\sin x} \over {{x^5}}}$
  • D
    None of these

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