Answer:
311 days
Explanation:
I(t) = 1.5 cos(2π/365 t) + 4.3
5.2 = 1.5 cos(2π/365 t) + 4.3
0.9 = 1.5 cos(2π/365 t)
0.6 = cos(2π/365 t)
2π/365 t = cos⁻¹(0.6)
2π/365 t = 0.927, 5.356
t ≈ 54, 311
First time is 54
Second time is 311
You plug in the numbers to get the answer.
cos⁻¹(0.6) = 2π/365t
0.927, 5.356 = 2π/365t
t = 54 or 311
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