Breathing is cyclic, and a full respiratory cycle from the beginning of inhalation to the end of exhalation takes about 7 seconds. The maximum rate of air flow into the lungs is about 0.5 Lls. This explains, in part, why the function f(t) : sin($) has often been used to model the rate of air flow into the lungs. Use this model to nd the volume of inhaled air in the lungs at time t. V(t) = liters