Answer:
216 days
Step-by-step explanation:
Converting the problem into mathematical terms
E(t) = {624}\sin\left({\maroonD{\dfrac{2\pi}{365}}}t\right) + {8736}E(t)=624sin(
365
2π
t)+8736E, left parenthesis, t, right parenthesis, equals, 624, sine, left parenthesis, start color #ca337c, start fraction, 2, pi, divided by, 365, end fraction, end color #ca337c, t, right parenthesis, plus, 8736 has a period of \dfrac{2\pi}{\maroonD{\scriptsize\dfrac{2\pi}{365}}}=365
365
2π
2π
=365start fraction, 2, pi, divided by, start color #ca337c, start fraction, 2, pi, divided by, 365, end fraction, end color #ca337c, end fraction, equals, 365 days.
We want to find the first solution to the equation E(t)=8400E(t)=8400E, left parenthesis, t, right parenthesis, equals, 8400 within the period 0<t<3650<t<3650, is less than, t, is less than, 365.