19. Determine the height of the lighthouse

From the top of an apartment of height 21 $m$, a boy observes the top of the lighthouse at an angle of elevation of 45$^{\circ}$ and the bottom of the lighthouse at an angle of depression of 30$^{\circ}$. Find the height of the lighthouse.

 

Answer:

 

The height of the lighthouse is 2136.37257.37256.372 $m$.