Question

I(t) models the daily solar irradiance, measured in kWh/m2-day on a farm, t days after the summer solstice. Here, t is entered in radians. I(t) = 1.5cos(2π/365*t)+4.3 What is the second time after the summer solstice that the solar irradiance is 5.2kWh/m2-day Round your final answer to the nearest whole day. ​ ​

Answer 1

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

Answer 2

First time is 54

Second time is 311

Explanation:

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