[填空题]
The angle of depression from a lookout at the top of a lighthous1;q aspfd* )w:mkfd-me (,4*bej dx .pscfk+ha,A) down to a bbdk.csjh,4a+p ,ef *xoat located at point C is $30^{\circ}$.
The boat travels towards the lighthouse and after 1 minute has travelled a distance of 50 m and is now located at point B. The angle of elevation from the boat at B up to the lighthouse lookout is $60^{\circ}$.
1.Write down the value of $x^{\circ}$ in the diagram. $^{\circ}$
2.Find the height of the lighthouse. m
3.Find the speed of the boat, in metres per second, from C to B. $ms^{-1}$
