A lifeguard is standing on the beach some distance from the shoreline, when he hears a swimmer calling for help. The swimmer is some distance offshore and also some lateral distance from the lifeguard. The lifeguard knows he can run twice as fast as he can swim. To minimize the time it takes to reach the swimmer, show that his path should consist of two line segments: relative to the shoreline, his running path should be at angle \(\theta_{1}\) and his swimming path should be at angle \(\theta_{2}\), where \(\cos \theta_{1}=2 \cos \theta_{2}\).