## 54. Group Activity Analysis of a Lighthouse
A rotating beacon L stands 3 m across the harbor from the nearest point P along a straight shoreline. As the light rotates, it forms an angle θ as shown in the figure, and illuminates a point Q on the same shoreline as P.
(a) Show that θ=tan−1(3x).
(b) Graph θ in the viewing window [−20,20] by [−90,90] using degree mode. What do negative values of x represent in the problem? What does a positive angle represent? A negative angle?
(c) Find θ when x=15.