If $\cos \alpha=\operatorname{sech} \beta$, then $\beta=$

• Correct answer
  A

  $\log (\sec \alpha+\tan \alpha)$
• B

  $\log (\sec \alpha-\tan \alpha)$
• C

  $\log (\sin \alpha+\cos \alpha)$
• D

  $\log (\cos \alpha+\cot \alpha)$

Hence, the correct answer is option: 'A'.