An aircraft is flying at a uniform speed v m/s. If the angle subtended at an observation point on the ground by two positions of the aircraft f second apart is $\mathrm{\theta }$, the height of the aircraft above the ground is given by

• A

  $\frac{\mathrm{vt}}{2\tan \mathrm{\theta }}$

• B

  $\frac{2\mathrm{vt}}{\tan \mathrm{\theta }}$

• C

  $\frac{\mathrm{vt}}{\tan (\mathrm{\theta }/2)}$

• D

  $\frac{\mathrm{vt}}{(2\tan \mathrm{\theta }/2)}$