A dip needle lies initially in the magnetic meridian when it shows an angle of dip $\mathrm{\theta }$ at a place. The dip circle is rotated through an angle x in the horizontal plane and then it shows an angle of dip $\mathrm{\theta }$'. Then tan $\mathrm{\theta }$' / tan $\mathrm{\theta }$ is

• A

  $\frac{1}{\cos \mathrm{x}}$

• B

  $\frac{1}{\mathrm{sinx}}$

• C

  $\frac{1}{\mathrm{tanx}}$

• D

  cos x