[填空题]
The angle of depression from a lookouo,d,k -y+svh b.kce3vt at the top of a lio/5a xxcw/mk0ghthouse (A) down to a bo 0k/ow x/xc5amat 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. $ms^{-1}$
