5.
A scuba diver and his crew on deck spot some dolphins jumping in and out of the water as they swim through the ocean. Let the function
represent the path that the dolphins travel, where x represents the time since the start of travel and y represents the dolphins' distance above and below the surface of water. The scuba diver and his crew monitored the dolphins for a 20 second interval. At what times (in seconds) during this 20 second interval were the dolphins at the surface level? (Hint: Look for when x equals zero.)