I found this problem confusing to setup and visualize. It says that Point A is the point on the shore closest to the beacon so that would be 2 miles from the beacon since the beacon is 2 miles from the shore. Then the question asks when the beam is lighting up a point 2 miles along the shore from point A. I think some hints are needed for this problem. To give a picture with A indicated in the picture and also give the fact that 1 rev/min = 2pi rad/min since some might not remember it from trigonometry.
See appliedRelatedRates/exercises/singVarCalcRelatedRates5.tex
https://ximera.osu.edu/mooculus/appliedRelatedRates/exercises/exerciseList/appliedRelatedRates/exercises/singVarCalcRelatedRates5
I found this problem confusing to setup and visualize. It says that Point A is the point on the shore closest to the beacon so that would be 2 miles from the beacon since the beacon is 2 miles from the shore. Then the question asks when the beam is lighting up a point 2 miles along the shore from point A. I think some hints are needed for this problem. To give a picture with A indicated in the picture and also give the fact that 1 rev/min = 2pi rad/min since some might not remember it from trigonometry.