Velocity of air during a cough According to B. F. Visser, the velocity v of air in the trachea during a cough is related to the radius r of the trachea according to
v = ar2(r0 - r)
where a is a constant and r0 is the radius of the trachea in a relaxed state.
Find the radius r that produces the maximum velocity of air in the trachea during a cough.