23. Five mark example problem X

From the top of a $12 \ m$ high building, the angle of elevation of the top of a cable tower is $60^{\circ}$ and the angle of depression of its foot is $30^{\circ}$. Determine the height of the tower.

 

Answer:

 

The height of the tower $=$  .

 

(Note: Enter the number in the first box and the unit (short form) in the second box.)