Solution
= Solution
Adding the three equations of the <SIR model with waning immunity> gives
$$
\frac{d}{dt}(S+I+R)=0.
$$
\b[Hence <conservation of population> holds: $N=S+I+R$ is an <integral of motion>.]
= Solution
Adding the three equations of the <SIR model with waning immunity> gives
$$
\frac{d}{dt}(S+I+R)=0.
$$
\b[Hence <conservation of population> holds: $N=S+I+R$ is an <integral of motion>.]