Breathing is cyclic and a full respiratory cycle from the beginning of inhalation to the end of exhalation takes about 5 s. the maximum rate of air flow into the lungs is about 0.4 l/s. this explains, in part, why the function f(t) = 2 5 sin(2πt/5) has often been used to model the rate of air flow into the lungs. use this model to find the volume of inhaled air in the lungs at time t.