4. Use a sine function to describe the height of the tides of the ocean if high tide raises the water level to 5 m and at noon and low tide drops it down to 1 m at 4 p.m. Let t = 0 be 12 noon.

For a person at rest, the velocity v (in liters per second) of airflow during a respiratory cycle (the time from the beginning of one breath to the beginning of the next) is modeled by v=0.85sint/3, where t is the time (in seconds). a Find the time for one full respiratory cycle. b Find the number of cycles per minute. c Sketch the graph of the velocity function. Use the graph to confirm your answer in part a by finding two times when new breaths begin. (Inhalation occurs when v0, and exhalation occurs when v0.)

Velocity at the Equator Assuming the radius of the earth is 4,000 miles, use the information from Problem 43 to find the linear velocity of a person standing on the equator.