Chapter 4.6, Problem 63E

The light in the lighthouse in Figure 4.102 rotates at 2 revolutions per minute. To calculate the speed at which the spot of light moves along the shore, it is best to differentiate:

$\begin{array}{l}(a)\text{}\text{}\text{}\text{}{r}^2=5^2+x^2(b)x=r\sin \theta \\ (c)x=5\tan \theta (d)r^2=2^2+x^2\end{array}$

Figure 4.102