Answer:
We readily separate the variables and integrate:
∫dP/P=∫(k+bcos2[tex]\pi[/tex]t)dt
ln P=kt+(b/2[tex]\pi[/tex])*sin2[tex]\pi[/tex]t+ln C
Clearly C = Po, so we find that P(t) = Poexp(kt + (b/2[tex]\pi[/tex])* sin 2[tex]\pi[/tex]t). The 271- curve with the typical numerical values P_o = 100, k = 0.03, and b = 0.06. It oscillates about the curve which represents natural growth with P_o and k = 0.03. We see that the two agree at the end of each full year.
note:
find the attached graph